“It Shouldn’t Be at All Surprising”: A Link Between Birth Control and Performance?

Chelsea LittleAugust 17, 20113

(Author’s Note: While some of the athletes and coaches contacted by FasterSkier for this story were willing to openly discuss birth control, many wished to remain anonymous rather than allow the public to make assumptions about their sexual choices, a desire that FasterSkier respected. For these sources, pseudonyms will be marked with an asterisk (*) the first time they appear, and they will subsequently be referred to by first name, rather than last name like the rest of the sources.)

Clare Egan representing UNH at the Lake Placid SuperTour last winter.

In 2006, Clare Egan was a successful high school athlete with a bright future. A member of the cross-country, nordic skiing, and track teams at Cape Elizabeth High School on the Maine coast, she won three state titles in track and skied to top-twenty finishes at the Junior Olympics her senior year. After that, she left home to attend Wellesley College, where she expected to continue her athletic success.

For a while, she did. Egan cut more than a minute off of her 5 k personal best in cross-country over the course of her freshman fall. But then, she began to fall apart.

“Starting the winter of my freshman year I had a decline in my athletic performance,” Egan told FasterSkier. “I went to Junior Olympics again and they were in Soldier Hollow [Utah]. I did really badly, especially compared to the year before, even though I was in theoretically better shape. I was very close to the back of the pack instead of being 13th and 14th.”

At the time, Egan blamed her results on the altitude, which can be a challenge for skiers from New England and other low-elevation areas.

But her performance continued to backslide. She had a disappointing track season in the spring, and in the fall of 2007, she was suddenly running in the 20-minute range for a 5 k instead of the 18:30’s she had raced her freshman year. Things got worse and worse. First, Egan thought that low iron was the culprit, even though she didn’t meet the clinical definition of anemia. Then she wondered if she was burnt out, so she took her entire junior year off from training and racing and studied abroad.

“That summer, before my senior year, I basically went through and I systematically resolved all of the problems that I thought I had,” Egan said. “I had taken a whole year off, so I couldn’t blame being burnt out. I got my iron back to totally fine levels, so I couldn’t blame the iron. I thought that maybe I wasn’t really training that well. So I did a lot of cross training. I upped my volume. I just did a much better job of summer training before my senior year than I had ever done before.”

Even after so much thought and preparation over the summer of 2009, Egan’s senior cross-country season was no better than her sophomore one.

“It was very hard for me to break 20 minutes in a 5 k,” Egan explained. “I always felt like I was able to push myself to 80 or 85 percent or so, and not beyond that. It was okay in a lot of workouts… I was able to run mile repeats at a fast pace, but I couldn’t do a race. Basically, I was not able to race. Racing is when you push yourself to 100 percent, and I could not do it. Within 800 meters, I would feel like I had totally reached my VO2Max, and couldn’t go any harder, and then I would just really suffer for the next three miles.”

Like a scientist doing an experiment, Egan had already examined all of the variables she thought could be affecting her performance, and she had controlled them. What could be the problem?

She began to form a hypothesis when she began suffering from stomach aches. She marked the days when her stomach hurt on the calendar, and noticed that they coincided with the first day of a new month of NuvaRing, a form of hormonal birth control she had been using since the August before she started college.

“I had never had any noticeable side effects before,” Egan said.

Although Egan had been racking her brain for months trying to explain her poor performance, she had ruled out birth control as a possible factor. After all, her freshman cross country season had been stellar even though she was already using NuvaRing. But when the side effects began showing up three years later, a light bulb went off in her head.

“I thought, okay, I’ve never had these before and they’re showing up after three years,” Egan said. “Maybe there are side effects that are creeping in.”

After more deliberation, she stopped using NuvaRing in October. That winter, skiing for Wellesley – which didn’t have a ski team until Egan arrived and started one, acting as both coach and athlete – she qualified for 2010 NCAA Championships, where she finished 25th in the skate race, the fourth woman from the East.

Egan also competed at D-III track and field championships that spring, where she finished 6th, was named an All-American, and tied the Wellesley College record for the 1,500 meters.

“If you look at my athletic performance, someone would say, ‘wow, is this person on drugs?’” Egan said.

Egan’s results on the trails have continued to impress: in 2011, she started graduate school and represented the University of New Hampshire at NCAA Championships for skiing, and she is now a member of the Craftsbury Green Racing Project, an elite post-collegiate team based in Vermont.

Most doctors say that birth control pills do not have any effect on athletic performance; some would argue that Egan was grasping at straws when she blamed her poor results on NuvaRing. But when she discontinued her use of hormonal contraceptives, Egan went from anonymity to success, and she is not the only skier who has had this experience. Which begs the question: why do so few people think that hormonal birth control can affect female athletes?

An Invisible Problem, or an Imaginary One?

Stories like Egan’s are just that: stories. There is little scientific evidence that the hormones in birth control have any effect on performance, positive or negative. So what can Egan – and the dozens of other female skiers who have had an experience like hers – do?

Perhaps, they can simply talk to their peers. According to the Center for Disease Control, seventeen percent of American women of childbearing age took oral birth control pills between 2006 and 2008. In young women, the numbers were even higher. A Thompson-Reuters study showed that more than one in four 18-year-olds were prescribed “the pill” in 2009, and according to the American College Health Association, forty percent of college women use oral contraceptives.

(NuvaRing, the vaginal insert Egan had been prescribed, is used by 1.5 million women worldwide. Because it uses the same kinds of synthetic estrogen and progestin as oral contraceptives, NuvaRing has the same side effects as the pill, and anything written about the pill in this article applies to the ring as well, unless otherwise noted.)

Of 123 female skiers and biathletes surveyed by FasterSkier, 71 percent had used hormonal birth control at some point. The majority of these women were never warned by their doctors that birth control could have an impact on their skiing careers – and in fact, in many cases, the opposite was true.

“My doctor told me that wasn’t a possibility,” said Jean*, a post-collegiate skier.

And yet of the 88 women who had used hormonal birth control, 44 percent believed that it had negatively affected their performance, although not always to the extent that Egan did.

Sara Studebaker racing at the Presque Isle World Cup in February.

“When I went off the pill, I lost weight and generally just felt like I was better able to handle training,” said 2010 Olympic biathlete Sara Studebaker. “Clearly there are several factors that could have impacted this as well, but I feel the pill definitely played a roll.”

For years, the medical community has batted questions about the safety of hormonal birth control back and forth. Does it increase the risk of breast cancer? Lead to infertility? Cause increased mortality? While the answers to these questions appear to be “no,” the effects of added hormones on the human body still aren’t fully understood – and the impact on athletic performance has barely been examined.

But that doesn’t mean that it doesn’t exist. For instance, use of the pill can lead to the development of blood clots, a life-threatening situation. They can affect an athlete’s mood, which can diminish their drive to train and compete. Hormonal birth control can lead to higher core body temperatures and changes in thermoregulation. Side effects like nausea and headaches can make training unpleasant or even impossible.

And then there are the stories, coming from skier after skier, about how their performance declined after they began using birth control pills, and improved when they stopped taking them. Without scientific proof that hormonal contraception caused these changes in results, the anecdotes are puzzling, but they shouldn’t be ignored.

Nevertheless, Jean’s experience was not unusual; many doctors don’t think that hormonal birth control has any effects on athletic performance.

Kristine Karlson, a family medicine doctor at the Dartmouth Hitchcock Medical Center in Hanover, New Hampshire who also specializes in sports medicine and happens to be a three-time World Champion in rowing, said that she informs her athletes about many side effects of birth control pills, but that decreased performance is not one of them.

“As far as I’m aware… I’m not aware of any studies that say, without a question, that this is causing trouble,” Karlson told FasterSkier. “Anecdotes are anecdotes, and what do you do with that? I don’t know.”

Given that the research hasn’t been ideal – there are few studies which address the topic, and the ones that exist are limited in scope – women are being left without much, other than anecdotes, to guide their decisions. However, there is no question that hormones play an important role in many aspects of physiology, some of which may affect athletic performance.

Sex, Drugs, and Sports

“From prepuberty through to… menopause and beyond, the female athlete is exposed to a constantly shifting kaleidoscope of endogenous sex steroid hormones,” a team of researchers led by Dr. Naama Constantini of Tel Aviv University noted in a 2005 paper. “Oral contraceptives… further introduce exogenous synthetic hormones to the equation.”

How, exactly, do those exogenous (from outside the body) hormones shift the equation? To answer that question, it’s important to have a basic understanding of the endogenous, or naturally-occurring, ones which they replace.

The female body is awash with hormones that regulate the menstrual cycle and reproduction; estrogen, progesterone, and testosterone have the strongest presence. For athletes, who usually try to avoid pregnancy, the main reminder that all of these hormones affect their lives is from their monthly period.

Most women dislike having their period, but Karlson said that in terms of athletics, there’s no reason to avoid it

“As far as I know, there’s no good evidence to say that having your period is going to affect your performance, that during your period your performance is going to be that much worse or better,” Karlson said.

The obvious exception is for women who suffer from premenstrual syndrome (PMS), defined as a range of physical and emotional symptoms occurring five to eleven days before menstruation, which can also lead to depression. Another exception is for those who have exceptional heavy periods with significant blood loss. For these women, training and competing are much more difficult during their periods.

There’s not much research showing that periods affect athletic results. For instance, one of the few studies showing a negative correlation used only six women as test subjects. But the menstrual cycle affects some aspects of physiology that could impact performance in more subtle ways.

For instance, women have been found to tear their anterior crucial ligaments (ACL’s) far more frequently in one phase of the menstrual cycle than the others. While there’s no definitive explanation for the correlation, researchers say that the most likely culprit is hormone concentrations.

The menstrual cycle is divided into three sections: the follicular phase, the ovulatory phase, and the luteal phase, all of which have their own signature hormone profiles.

  • The follicular phase begins the cycle and lasts about nine days, during which estrogen levels slowly increase.
  • Then, after a spike in estrogen, a woman ovulates, or releases an egg. The ovulatory phase lasts about five days.
  • During the luteal phase – the rest of the 28-day cycle – the egg, now called a corpus luteum, releases progesterone until it is flushed from the body during a woman’s period; hormone levels return to baseline.

So over the course of a month-long cycle, hormone levels and ratios can change dramatically, from the low levels of both hormones at the beginning of the cycle through the high estrogen levels in the ovulatory phase and then the corresponding increase in progesterone during the luteal phase.

“There appears to be a consensus emerging from the literature that the likelihood of incurring an ACL injury does not remain constant during the menstrual cycle, with a significantly greater risk during the preovulatory [follicular] phase than during the postovulatory phase,” an International Olympic Committee (IOC) panel wrote in 2008.

A generalized depiction of the changes in hormone concentrations through a 28-day menstrual cycle.

While ACL tears are extremely rare in the nordic world, the panel’s conclusions are far from irrelevant for skiers and biathletes. One component of the findings was that since hormone profiles are unique to each woman and can vary greatly, some women may be at greater risk for injury as the ratios of estrogen and progesterone seesaw in their bodies.

And although the panel was concerned about the hormones’ impact on ligament injuries, the ACL is only one of the many aspects of physiology that is influenced by naturally-occurring hormones. For example is that core body temperature rises between 0.3 and 0.5 degrees Celsius when progesterone is released during the luteal phase. This reduces the body’s ability to defend itself against heat; female athletes are more easily fatigued in hot weather during the luteal phase, which can affect both training and competition.

Among other physiological contributions, estrogen has significant effects on the cardiovascular system, while progesterone is a controlling factor in some aspects of respiration.  Estrogen and progestin might sometimes counteract one another, but in other instances they might have additive effects.

How, exactly, do they shift the equation? That is far from fully understood, although some data has been collected. For example, a team of researchers at San Diego State University published a paper in 1997 showing that women using oral contraceptives experienced a larger core temperature increase and higher heart rates after exercising in the heat than women who were not taking the pills.

But overall, there isn’t much research about the effects of hormonal birth control, despite the large percentage of women who take it. Even when it comes to ACL injuries, which get a lot of attention, doctors aren’t sure whether shifting hormone concentrations with contraceptives might change the likelihood of injury.

“There is a paucity of clinical research examining these effects in women who… use contraceptive hormones, and who represent a large percentage of the physically active female population,” the IOC panel noted, adding that future studies should investigate the effects of oral contraceptives on musculoskeletal tissue.

What’s in a Pill?

On a most basic level, birth control pills consist of synthetic, or exogenous, hormones which mimic the natural, or endogenous, ones in a woman’s body. Hormonal contraception works by overriding the body’s natural cycle; hormone production is more or less shut down, and eggs are no longer released from the ovary.

“The pill” was first introduced in the United States in 1960. At that point, it contained 100 to 175 milligrams of estrogen and 10 milligrams of progestin, the synthetic equivalent of progesterone. The strategy with these early pills was to trick the body into thinking it was pregnant so that it would not ovulate.

“When you’re taking an oral contraceptive, the levels that you are maintaining day to day to day are quite different than the fluctuating levels that occur during a normal menstrual cycle,” said Witters.

Over the years, the amount of estrogen and progestin in birth control pills has steadily decreased in an attempt to reduce side effects. (In the 1970’s, rumors that the pill led to breast cancer created a backlash against it.) Today, most pills contain only 30 to 35 milligrams of estrogen, and some low-dose formulas have only 20 milligrams. “Mini-pills”, a slightly less effective formulation, contain only progesterone.

“All of the birth control pills we use now are the lowest possible doses that we can get away with because of the whole side effect thing,” said Karlson, the sports medicine doctor.

Regular pills and NuvaRing are both based on synthetic estrogen, which despite being chemically different than the naturally-occurring estrogens, binds with estrogen receptors in the body.

Estrogen has wide-ranging effects beyond simply regulating the reproductive system: it can function on the metabolism, fat stores, protein synthesis, muscle growth, bone reabsorption, blood coagulation, and salt retention, among other aspects of physiology.

Just how many other aspects? A team of researchers from Illinois and Singapore identified over 1,000 estrogen receptor binding sites in the human genome. While this doesn’t mean that there are 1,000 genes controlled by estrogen – not every binding site leads to a change in gene expression – it does indicate that the hormone regulates a lot of different things. It also means that ethinyl estradiol, the synthetic hormone, likely does much more in a woman’s body than simply stopping ovulation.

A variety of different synthetic progestins are used to mimic progesterone in birth control pills. They are derived from different sources, metabolize differently in the body, and interact with the hormone receptors to varying degrees. They carry different side effects, which is one reason why doctors sometimes prescribe women a different brand of pill if they don’t like their original prescription.

Like estrogen, progesterone controls more than just the reproductive system. A team of researchers from California noted in a 2008 paper that there are progesterone receptors throughout the brain and in every type of neural cell. So like synthetic estrogen, progestins have the ability to influence a large number of physiological functions.

There hasn’t been much conclusive research about the long-term effects of any of these synthetic hormones. But researchers have hypothesized that even slight differences in their structure can influence how the molecules act in the body.

“It shouldn’t be at all surprising if one saw differences from exogenous estrogen and progestin versus the endogenous ones,” said Witters, the endocrinology professor.

Dreams Deferred, and Testosterone Depressed

Like Egan, Connie* began using hormonal birth control just before she went to college. And like Egan, she had been a standout high school racer, winning her state championship and excelling at Junior Olympics, where she had stood on the podium and notched other top-ten results. Connie was poised for a successful college career.

She attended a school with a strong ski program, and her freshman year, she didn’t have any standout results, instead blending in with the team’s other above-average racers. At the time, she figured that it was just the freshman curse – many athletes have less than stellar results as they begin college and are faced with living on their own, balancing school and social life, and other new experiences.

But even as Connie grew older and figured college out, her racing still stagnated. She was frustrated, because she was sure she could be a great skier; although she was a solid varsity member of her team, her results didn’t match up to the potential she had showed as a junior athlete.

Then, one spring, she stopped taking Yaz, her birth control pill.

Things changed.

“All of a sudden I could run up hills, and keep running, fast, for a long time,” Connie told FasterSkier.

Like Egan, Connie said she had felt slow and bogged down while she was using hormonal birth control. She described how she would start running or skiing in a full-bore workout, and a few minutes later feel like her legs were filled with lactic acid, preventing her from pushing at full capacity. After she stopped taking Yaz, she felt like she was “back to normal.”

But unlike Egan, Connie hadn’t gone through an elaborate review of what could be hurting her performance, and even after she improved – she went on to be one of the best racers in her region, and race after college – she was reluctant to blame birth control outright for the less outstanding performances earlier in her college career.

“I was a lot more relaxed in general, and so that might have had something to do with my improvement,” Connie said.

None of Connie’s coaches had warned her that her performance might be affected by the pills, and neither had her doctors, who had only talked about the more commonplace side effects. She had been told that she’d probably have less acne, but that she might gain weight, and her breasts might grow. For Connie, birth control pills didn’t seem to have any drawbacks until she stopped taking them and her results improved dramatically.

After the fact, she talked to another doctor. Connie still wasn’t sure whether birth control explained the change in her fortunes as a skier, but she was starting to get curious. Taking hormonal birth control, the new doctor said, can lower women’s testosterone levels. And if Connie was an athlete whose body relied on testosterone to perform, he said, then this might be why she had struggled.

Egan also received this explanation after seeking out a knowledgeable doctor. The theory, based on a study published in 2006 by researchers from Boston University, is that long-term use of hormonal birth control leads to higher production of sex-hormone binding globulin (SHBG).

This protein binds to sex hormones like testosterone, making them unavailable for the body to use. The study found that women who had been taking birth control pills had four times the amount of SHBG that non-users were producing; as a consequence, there was much less testosterone available for their bodies to use. Perhaps even more importantly, for women who had used birth control pills but then stopped, SHBG levels did not return to normal – they stayed high, indicating that there was the potential for long-term effects on testosterone.

Luckily for Connie, she didn’t suffer any noticeable long-term effects from Yaz. She was happy with her college experience and had the chance to be a full-time athlete after graduating.


What Connie didn’t know until later was that poor athletic performance wasn’t such a bad outcome compared to the experience of some other women who were using Yaz.

Yaz was approved by the Food and Drug Administration (FDA) in 2006, and Bayer, the manufacturer, began promoting it heavily, especially to young women. The drug contained a low dose of estrogen compared to many birth control pills, and Bayer also claimed that it would help with acne and pre-menstrual depression (PMDD). Within a few years, Yaz became the best-selling birth control pill in the U.S.

The drug used the same synthetic form of estrogen as other birth control pills, but its form of synthetic progestin, drospirenone, was unique and had only been used in Yasmin, a higher-estrogen pill that had been approved in 2001. Unlike the other progestins which had been included in birth control since the 1990’s, the newer synthetic hormone didn’t have years of testing behind it.

This turned out to be a big problem. As early as 2007, women were complaining about Yaz – they had many side effects ranging from weight gain to depression to headaches to nausea to high potassium and even blood clots. As the years went by, more and more cases of extreme side effects cropped up. Although numbers are hard to confirm, there are between 50 and 200 reported deaths of mostly young women who were taking the pill.

No skiers have died from taking Yaz, but they did experience some of the extreme side effects.

One senior racer said she experienced “drastic depressed mood effect from the pills,” while a college racer wrote in the FasterSkier survey that she was easily tired, didn’t feel a competitive drive to train or race, and couldn’t ski or run with the same intensity as when she was not taking the pills. A third skier said that she became very light-headed when she raced and her sodium level plummeted.

When a fourth skier was asked about how Yaz affected her athletic performance, she simply wrote, “VERY negatively, with more and more negative effects over time.”

Yaz was so bad that it drew attention for more than just its effects on athletes. In both 2008 and 2009, the Food and Drug Administration (FDA) slapped Bayer with citations.

“YAZ has additional risks because it contains the progestin, drospirenone . . . which may result in potentially serious heart and health problems,” the FDA wrote in their 2008 warning to Bayer.

In 2009, the problems with Yaz gained national prominence when the New York Times published an article about women who had developed blood clots while on the pill. At the beginning of August this year, the online Huffington Post ran an editorial calling on the FDA to conduct stronger oversight on the ways in which drugs are marketed, citing Yaz as one of the primary examples of how the process can go wrong.

To date, more than 7,000 lawsuits have been filed against Bayer by women who suffered serious side effects from Yaz. Yet Bayer is still trying to project a squeaky-clean image for its drug. How? More marketing, for one thing. But they’ve also infiltrated the scientific record.

Preliminary research on the side effects of drospirenone will lead the curious to a large European study showing no increase in the risk of blood clots, high potassium, or other dangerous side effects. At first, it seems like the American statistics about deaths might have been fudged by headline-chasing trial lawyers. But then a secret emerges: the European cohort study was sponsored by Bayer, the manufacturer.

“Increased venous thromboembolism [blood clot] risk is associated with any [oral contraceptive] and Bayer is committed to studying the safety and efficacy of our products,” said Dr. Leo Plouffe in a press release from Bayer, where he is the Vice President of Medical Affairs and Women’s Health.

“Bayer’s assessment that its drospirenone-containing [pills] are safe and effective,” he stated in another release.

Others beg to differ.

As more research has been done, independent studies have found that Yaz and other drospirenone-based oral contraceptives do have increased risks. For instance, a study published this year in the British Medical Journal reported an almost threefold increase in the incidence of blood clots for women using the pills compared to those taking a contraceptive containing a different kind of progestin.

Bayer has worked to minimize the implications of that research.

“Bayer’s assessment, based on its review to date, is that the manner in which the authors applied the study methodology reported in these two publications show significant flaws and the databases used provide less reliable conclusions than are available from existing scientific evidence,” the company said in a press release.

While Bayer and independent scientists are arguing, a number of skiers are left picking up the pieces after bad experiences with Yaz.

“I wasn’t as fit-feeling even though I was training well,” one NCAA Championships competitor said. “I was emotional and lethargic. I noticed the negative effects once I went off – immediately I was feeling more normal, but four months later was when I really felt like I was back to being myself as a ski racer and a regular person.”

In all, ten of the fifteen Yaz and Yazmin users surveyed by FasterSkier said that they thought the pill had negatively affected their performance; all of them had stopped taking the drug at some point and seen their results improve.

They were luckier than a lot of other women across the country – none of them came close to death caused by an unsafe birth control pill.

Side Effects and Sports

There’s no way of knowing whether Connie’s testosterone was actually lower when she was taking Yaz, but if it was, it’s symptomatic of the way that most skiers experience the impact of hormonal birth control: through invisible, inexplicable changes. There’s little proof that hormonal contraceptives change big metrics like VO2Max or affect how a woman can handle lactic acid.

For instance, although scientists have discussed whether birth control hormones can lower VO2Max, most studies haven’t found this to be true. Many of the studies that sparked this claim were done using older types of birth control pills with much higher doses of hormones. More recent research is divided in its findings, and none of the studies used highly-trained athletes.

“The research is just crappy,” said Witters, the Dartmouth professor. “It’s surprising.”

As with aerobic capacity, there have been conflicting results about whether using hormonal contraceptives influences an athlete’s ability to add muscle mass.

A team of Texas A&M researchers published a paper in 2009 showing that non-trained young women using birth control pills had a much harder time gaining lean muscle compared to those not taking pills. But even the researchers themselves were unsure whether their results meant that there would be significant impacts on performance.

Nevertheless, it got enough press that a few skiers had heard of it.

“I read in a magazine that birth control could affect your muscle growth,” one college racer said. “I hadn’t been improving in the weight room in the two years since I’d been on birth control, but after going off of birth control my performance in the weight room and in general increased substantially.”

Many other papers have reported that hormonal birth control had no noticeable effect on muscle growth, and as with aerobic capacity, none of the research has been done with elite-level athletes – in fact, most of the studies have focused on “active” women who spend much less time exercising than the typical cross-country skier.

But even if birth control pills haven’t been shown to change specific athletic metrics, the seemingly minor side effects that are a risk for all women can still have a big impact on athletes.

In a world where everything from training to eating to sleeping is carefully monitored and planned to optimize performance, even seemingly insignificant side effects could make it harder to produce a top performance, some of the survey respondents surmised. Most of the side effects of hormonal birth control seem harmless, if inconvenient: mood changes, larger breasts, and occasional nausea or headaches during menstruation.

“I think the birth control affected me as it suggests it may affect females: upset stomach, nauseous, feeling sluggish,” one post-collegiate racer wrote in the survey. “This in turn affected my everyday life- I didn’t feel as good doing things like working, training, etc. The birth control itself did not alter ski performance; the other factors did this.”

While these minor side effects can slow an athlete down, the thing that most skiers and coaches are concerned about is weight gain, which has long been listed along with the pill’s other side effects.

“My club coach in high school told me never to go on birth control because it would make me fat and slow,” another college skier told FasterSkier.

Not all pill users experience weight gain, and in fact, most studies on the topic show that it isn’t even caused by hormonal contraception. Two recent papers published in the journal Human Reproduction tackled the issue from different angles.

In the first, a team of Swedish researchers followed a cohort of women starting in 1986, when the test subjects were 19 years old. The scientists found that use of oral contraceptives had no effect on weight gain, and that in fact age was the main predictor of weight – in other words, all of the women gained weight, not just those taking birth control pills.

The other paper was written by a team from Oregon which used rhesus monkeys in an experiment. They found that giving the monkeys birth control pills did not increase their weight, and in obese monkeys it actually lowered body weight

In addition, 2008 study at the University of Massachusetts looked specifically at this issue in athletics. At the end of the trial, the team wrote that oral contraceptives did not cause the athletes to gain either weight or body fat.

But despite the scientific evidence, a 2010 survey showed that 61 percent of American women between the ages of 18 and 35 believed that birth control pills caused weight gain. Several more athletes told FasterSkier that they had been warned by doctors, coaches, and teammates that using hormonal birth control would make them gain weight. Others, including 2010 Olympian Studebaker, confirmed that they had gained weight while using the pill.

The whole suite of side effects has impacted skiers in different ways.

“Whenever the levels of hormones in the birth control changed I would spend the entire day throwing up,” one high school skier wrote in an e-mail. “I was unable to train and I often got tired.”

“I think my training was affected,” Alyssa Devlin, a member of the Harvard ski team, told FasterSkier. “The pill gave me bad cramps, interrupting some interval sessions. It also made my breasts grow, making running not quite as easy as it used to be.”

Still, most doctors would say that the majority of women are unaffected by these problems, and for those who are, it’s simple enough to go off the pill.

Living Dangerously

A Sprint Cup podium almost didn't happen for Kikkan Randall after a health scare in 2008.

While Yaz is proving to be one of the most dangerous birth control pills on the market, nearly all of the hormonal contraceptives carry one big risk: blood clots. Consider the case of Kikkan Randall.

In late March 2008, the Olympian went to the doctor because she was having back pain, and was surprised to learn that she had a massive blood clot in her leg. Randall immediately underwent a procedure in which physicians inserted a catheter into one of her veins and sprayed a thinning agent to disintegrate the clot. Randall’s blood clot was so large that she had to have three surgeries and ended up spending more than a week in the hospital before the clot was cleared completely.

The condition Randall was suffering from is called deep vein thrombosis (DVT), and it affects a startling number of young, active, otherwise very healthy women. Blood clots develop more frequently in the legs, where blood is flowing more slowly, and they often are a result of an injury to a blood vessel.

There are several risk factors which increase the likelihood of developing DVT: May-Thurner syndrome, when a vein near the pelvis is compressed; the genetic disorder Factor V Leiden, which affects five to seven percent of the Caucasian population; long plane trips; and the use of hormonal birth control.

Soon after the blood clot was found, Randall learned that she was a carrier for Factor V Leiden; she has also been diagnosed with May-Thurner syndrome. And as for the long plane rides? Pretty much unavoidable for World Cup athletes.

To make matters worse, Randall had been using NuvaRing, the same form of hormonal birth control used by Egan, the skier who opened this story, making her a perfect candidate for DVT.

“[DVT] never even came up [when I was prescribed NuvaRing],” Randall told FasterSkier.

The estrogen in birth control can boost several factors that help blood form clots. Progestin, for its part, relaxes blood vessels, meaning that there are more opportunities for blood to pool. Together, these two hormones lead to a major increase in the risk of DVT; researchers have found numbers ranging from two-fold to five-fold jumps.

The risk factors have an interactive effect, too. A 1995 study from the Netherlands found that women who were carriers for Factor V Leiden were 50 times more likely to suffer from a thrombosis if they used hormonal birth control.

“I was never tested to see if I had this clotting factor, understandably I guess – it occurs in such a small percentage of the population that it’s not really cost-effective to test everybody,” Randall said. “But given that it increases your clotting factor by forty times or something like that it’s also a little scary that they do just hand out [pills] like candy.”

Even though she displayed many of the other risk factors, Randall believed that birth control was the biggest cause of her blood clot. She pointed out that until she had started using NuvaRing, she had been traveling a lot and had already developed May-Thurner syndrome and Factor V Leiden, but hadn’t had problems with blood clots.

Kikkan Randall racing at 2011 World Championships.

“I think for sure that [birth control] was the biggest factor,” Randall told FasterSkier. “I think all of those other things… it was definitely the NuvaRing that kicked it over the top.”

To decrease the likelihood of developing another clot in the future, Randall stopped using hormonal birth control.

Although she was hospitalized and missed some spring training that year, Randall was lucky because the clot was discovered before it traveled somewhere else in her body. The Center for Disease Control reports that DVT and its variants, like pulmonary embolism, in which the clot is carried through the bloodstream to the lungs, strike approximately 300,000 to 600,000 American women each year. Between 60,000 and 100,000 of those women die.

Just this March, tennis superstar Serena Williams had to undergo emergency surgery after she suffered a pulmonary embolism. The condition results in immediate death in about a quarter of its victims.

While most people think that blood clots can’t happen to young, healthy athletes, that simply isn’t true. Besides the high-profile cases involving Randall and Williams, an NCAA All-American told FasterSkier that she had developed thrombosis after beginning to take birth control pills, and is no longer using them.

Besides the risk factors present for the average woman, athletes have a few more to contend with. Low resting heart rates, which are typical of many endurance athletes, mean that blood is moving slowly and has time to coagulate. In addition, strong muscles can compress veins – some researchers have hypothesized that this is one cause of May-Thurner syndrome.

“You hear about athletes who travel, long plane trips to Asia, and end up with a blood clot in their leg which is attributed to possibly family history, and complicated by her being on a birth control pill,” said Karlson, the sports medicine doctor. “Everyone I start on a birth control pill, I’ll ask them whether they have a family history of blood clots. Because that’s sort of a first hint.”

Britain’s Royal College for Obstetricians and Gynecologists stressed in its 2010 report on contraceptives and DVT that the condition was still rare, and that women on hormonal birth control should be aware, not alarmed.

“Although the relative risks of venous thromboembolism do increase with combined hormonal contraceptive use, the absolute risk in women of reproductive age is very low,” the College wrote in its 2010 Guidelines.

These days, Randall is winning races on the World Cup circuit – and she’s embroiled in a national lawsuit against Merck, the manufacturer of NuvaRing. Like Bayer, Merck was not entirely upfront with patients about the risks its product carried.

“It has kind of come to light that the company that produces NuvaRing has had some shady trials where they kind of put some results under the rug until they got the results they wanted,” Randall said. “It turned out to be far more dangerous than other things on the market.”

The Pill’s Many Purposes: Contraception and the Female Athlete Triad

One reason that it is so important to understand the effects of hormonal birth control on athletes is that many young women are prescribed the pills not only for contraception, but also to preserve bone mass.

“As an athlete, I never got my period, so I was put on the pill to get it at 17…. My doctor was worried that my bones weren’t getting enough nutrients, like estrogen and calcium, that women naturally get from menstruation, and which protect their bones and keep them away from stress fractures and osteoporosis,” former junior national medalist Julia* told FasterSkier. “And it worked.”

Menstruation and osteoporosis are connected through a syndrome called the female athlete triad, which affects many women, not just endurance athletes. However, it is more prevalent in elite athletes than the general public, and is most common in sports which emphasize leanness, such as running, cycling, skiing, figure skating, and gymnastics.

The triad consists of three interrelated problems: eating disorders or negative energy balance (when less energy is consumed than expended), skipped periods or the complete loss of periods (amenorrhea), and low bone mass. Some women display extreme symptoms of the triad, while others show intermediate symptoms, such as “disordered eating” rather than a clinical eating disorder. Others have a reduced frequency of periods, rather than completely losing them.

The three conditions which form the triad are closely related. Negative energy balance and poor nutrition lead to changes in the menstrual cycle and skipped periods; amenorrhea leads to lower estrogen levels in the body, which contribute to bone loss. So if a woman shows one symptom of the triad, it is likely that she is affected by the other components as well.

As a result, doctors become concerned when a female athlete says that she is skipping periods. Decreased bone density can lead to osteoporosis, when the body fails to form new bone or reabsorbs existing bone. Osteoporosis is a chronic disease and leads to more frequent fractures. According to the International Osteoporosis Foundation, at least two-thirds of the 30,000 hip fractures which occur in the United States each year are caused by the disease.

“The injury most associated with eating disorders in sports like cross-country and ballet is the stress fracture, which stems from the decrease in bone density that is a part of the female athlete triad,” said Meredith Curtis, a medical student at the University of Pennsylvania who studied the female athlete triad in cross-country runners when she was an undergraduate.

“Interestingly, this isn’t true for other sports which may also promote disordered eating like gymnastics, because the athletes put different stresses on their bodies that actually promote bone growth. All the high impact [in gymnastics] is really good for building strong bone, whereas runners and ballet dancers have a lot of low-impact, high-repetition stress on the bone that is hard on it.”

As athletes in one of these low-impact, high-repetition sports, how can skiers avoid injury? That’s where the pills come in.

In an effort to boost hormone levels in these women’s bodies and stop the loss of bone density, doctors for many years prescribed hormonal birth control, hoping that the exogenous hormones would do what the diminishing endogenous ones could not.

“The bottom line is that once you have osteoporosis, it’s very hard to fix your bones,” Karlson, the doctor from Dartmouth-Hitchcock, told FasterSkier. “So we’re really trying to preserve bone mass by giving back the hormones that you’re missing.”

The strategy made sense to doctors, who had been prescribing menopausal women with estrogen for the same reasons.

“There obviously is a parallel of estrogen deficiency in other circumstances, namely with respect to bone disease in the post-menopausal woman or the anorexic woman,” said Witters, the endocrinology professor. “It made perfect sense to say, let’s just give estrogen and that will correct this tendency to osteoporosis.”

And so more and more women have had the same experience as Julia, the junior national medalist.

“Athletic doctors have actually recommended birth control to me as a way of artificially forcing a period,” one former World Junior Championships team member told FasterSkier.

However, according to Witters, there is little evidence to suggest that replacing hormones in younger women is effective in preventing bone loss.

“In a relatively small number of studies, to be fair, when one is given estrogen, one does not see the achievement of normal bone density,” Witters said, referring to the lack of research into the subject. “So I think it is a myth that [birth control] protects oneself against bone loss or stress fractures.”

Curtis explained that some of the bone loss which resulted from the female athlete triad might not even be caused by low estrogen.

“[Researchers] think that the eating disorder is the root cause of the decrease in bone mineral density,” she wrote in an e-mail. “Losing some of the nutrients in a balanced diet may have direct detrimental effects on the bone, irrespective of whether the woman also has low estrogen levels because her reproductive axis is suppressed.”

Karlson said that she had stopped prescribing hormonal contraceptives for women who were skipping periods – unless they needed them for birth control – and was focusing on other aspects of health to solve the problem.

“The folks who are really looking at the literature are saying, ‘maybe this isn’t really the answer,’” Karlson told FasterSkier. “The real answer to actually getting your periods back is, well, getting your periods back, which means changing your energy balance, which means that a little more calories, even without weight gain, can help to regulate your periods again.”

This sentiment was echoed by U.S. Ski Team Women’s Coach Matt Whitcomb, who said that his staff was aware of the female athlete triad and encouraged athletes to address it by eating healthy – and enough.

Matt Whitcomb coaches the top U.S. women.

“Hormone regulation can be difficult for many reasons, but perhaps most commonly with endurance athletes it may be due to low available energy,” Whitcomb wrote in an e-mail. “This balance may be restored with the use of birth control medication, but it may also be restored by increasing the available energy. Each case is individual.”

Whitcomb hoped that more coaches around the country would become aware of the challenges presented by the female athlete triad.

“Long-term health should be prioritized over performance with regards to training any athlete,” he said.

For Julia, the contraceptives were a solution to skipped periods. She said she stopped taking the pills this winter, and her periods disappeared. But if Karlson is right, Julia might not have been any healthier on the pill than she will be off it – and in another few years, athletes in her situation may not be prescribed hormonal contraceptives in the first place.

For now, though, a number of young women are enduring the side effects of the pill, even if they don’t use it for contraception.

The Missing Link: Education

Not all female athletes are educated about female health issues, much less about the side effects of hormonal birth control, so they can’t always make informed decisions.

For instance, Curtis, the University of Pennsylvania medical student, said that when she was researching the female athlete triad in cross-country runners back in 2006, many of the women she talked to were unaware of the concept.

“I surveyed 150 college runners on cross-country teams,” she said. “They had some awareness of the fact that amenorrhea was a problem but many – almost half – had not heard of the female athlete triad. Those that had often heard from teammates and not from trainers and coaches, which points to a need for more education.”

Of the 123 women who responded to the FasterSkier survey, only 21 had been warned about any potential performance effects of birth control pills by their doctors or coaches.

Jessica*, a former U23 World Championship team member, suggested that male coaches in particular did not want to approach the birth control issue.

“I have only had about two female coaches compared to about eight male coaches,” she explained. “Almost all of them have been men who relate very well to women as well as men. The problem is, no matter how much female emotion they seem to connect to, there are some topics that no man wants to talk about, listen to, or know anything about. Some of these include birth control, periods, body image issues, relationship stress, and eating disorders.”

For high school athletes, talking with a coach about birth control and sex may be inappropriate, or at the very least uncomfortable; one of the nation’s top junior coaches said that he had not discussed birth control with his athletes and had only ever talked about it with one other coach.

Even coaches of more mature skiers seem to shy away from discussing an awkward topic, as evidenced by the dozens of skiers – including Connie, whose racing had stagnated while she took Yaz – who said they had never discussed contraception with their coaches.

Sometimes, coaches and other support staff just don’t feel like the issue is in their jurisdiction. For instance, Ed Merrens, the doctor for the U.S. Biathlon Association, said that he did not usually discuss birth control with his national team athletes.

“Most of the women I have been working with have had to make this decision a while back and not in their late 20’s, so by the time I work with them, they’ve sorted out the decision on what to use for birth control and what formula works best for them,” he explained.

But some coaches are trying to address the birth control issue. One male college coach said that he and his assistant were perfectly comfortable talking about contraception with their athletes.

“I’ve had athletes who it has affected pretty heavily,” said Joe*. “It was an enormous difference pre-birth control to post-birth control… Because unless you’re aware of birth control as a possible cause for poor performance, my experience is that an athlete will start going south for no real reason, and the athlete won’t even know the cause.”

Joe felt that he could be a better coach if he knew whether his athletes were hormonal contraceptives, so he said he made sure that the team atmosphere made those discussions comfortable and possible for his female athletes.

Another college coach, Grace*, said that she had gained weight and slowed down while taking birth control pills during her own ski career, and several of Grace’s athletes said that they had discussed birth control with her.

Jessica, who had lamented the lack of female coaches at high-level ski teams, thought that more skiers should be able to have open coach-athlete relationships, like the ones Grace and Joe had with their teams, and that with more female coaches women might be more likely to discuss topics like birth control.

“We need some more professional woman coaches and women with sports medicine backgrounds who women can contact about these kinds of issues,” Jessica wrote in an e-mail.

One Last Tale

While most of the women who responded to FasterSkier’s survey hadn’t talked about birth control with their coaches, roughly a quarter had discussed it amongst teammates. In many cases, this made them wary of using synthetic hormones.

Lynn* had heard from college teammates and friends that birth control pills could hurt her skiing, so when she went to a doctor in search of a low-hormone pill, she specifically asked about the interaction between birth control and athletic performance.

“When I initially had this conversation with my doctor, I told her I was hesitant to try it because of all the side effects and horror stories I had read and heard about, especially from other athletes,” Lynn told FasterSkier. “She seemed so nonchalant about prescribing such a powerful dosage of hormones that clearly has a strong affect on the majority of patients.”

Despite having reservations, Lynn decided to go ahead and try taking birth control pills.

“Other than hearing about some people’s bad experiences with birth control, no one discussed the possibility that birth control could negatively affect my athletic performance,” she said. “When I had heard negative reviews, people always said that it works differently for everyone and that you won’t know until you try.”

So try she did. Lynn’s doctor prescribed her Yaz.

Like Connie, Lynn didn’t really realize that Yaz was causing problems until she stopped taking it. But she hadn’t been herself since she started taking the pills. She said she started having huge mood swings: sometimes she was elated, and then she’d be severely depressed.

“The lows seemed to overpower the highs, as I was often extremely emotional,” Lynn said.

When she was feeling depressed, she didn’t care about anything: not ski racing, and not school. Her test scores dropped and she couldn’t muster the effort to do anything about it. She wanted to quit skiing.

“I suddenly didn’t care if I was first or last,” she said. “It was terrible.”

Even though she had heard stories about other women who had been affected by hormonal birth control, she still didn’t connect the dots.

“I looked for support in various people that I thought could help,” Lynn said. “My mom, my boyfriend, my closest girlfriends, my teammates, my coaches, etc.  People sensed that something was ‘wrong’ with me, but I had a hard time figuring out what it was. I went to my coach as an emotional wreck. I was overwhelmed with emotional stress and I couldn’t figure out where it was rooted.”

While her mood swings and depression were her biggest problem, Lynn also couldn’t go hard in workouts or races. She never felt well-rested and her pain tolerance had decreased; all of a sudden she would stop trying when things got hard.

Finally, she switched to a different form of birth control, and her symptoms subsided. She said she still experiences side effects, but they are nothing like what she felt while she was taking Yaz.

These days, she has a strong opinion about hormonal birth control: she feels cheated.

“I didn’t know at the time that [so many problems] could have been caused by the absurd amount of artificial hormones I was prescribed,” Lynn said.

But Lynn had more information about birth control than three quarters of FasterSkier’s survey respondents – she had the stories from her friends and teammates. If even Lynn still ended up in a situation where a pill made her want to quit skiing, what’s a girl to do?

“You’re a Special Case”: Ask Questions

Kikkan Randall: "Talk to your doctor"

That’s a question that nobody seems able to answer, and they probably won’t any time soon.

The gold standard of medical testing is the double-blind study, in which neither the researcher nor the test subject know whether they are receiving the drug in question or a placebo. The few studies looking at hormonal birth control and endurance athletes have not been double-blind; they were instead observational, using a group of women who knew they were taking a birth control pill, and a group of women who weren’t taking anything.

One reason for this is that it’s problematic to tell a woman that she can’t become pregnant, and then hand her a sugar pill with no contraceptive benefits.

“In randomized clinical trials, there are ethical considerations since patients are allocated by a random mechanism to either a control group in which the patient receives a standard procedure or into an experimental group where the outcome may be uncertain,” wrote University of Sydney researcher Edith Weisberg in a 1986 paper on how to design studies of birth control pills.

The clinical trials which allowed each drug to get approved by the FDA were double-blind. But beyond that, the moral considerations have added one more item to an already-long list of difficulties for researchers who want to study birth control and sports.

Another issue is that well-designed medical studies control as many variables as possible, and that’s difficult when working with elite athletes. In the case of hormonal contraception and skiing, each athlete has her own training plan and her own goals, so differences in results wouldn’t be due solely to hormonal contraception. Yet separating the women from their teams and disrupting their training probably wouldn’t attract many test subjects.

But even without the rock-solid evidence provided by a double-blind study, there are some guidelines that seem to have drawn a consensus – for instance, Yaz or other birth control formulations that contain drospirenone should be avoided. Women shouldn’t use hormonal birth control if they show other risk factors for DVT. And above all, they shouldn’t take birth control pills if they don’t need them – even if they are skipping their periods.

Outside of those recommendations, it’s not wise to simply tell athletes to stop using hormonal birth control when it has other benefits unrelated to athletic performance.

“I don’t have any doubt that there might be effects on respiration, effects on cardiac function, effects on blood pressure, effects on lots of things,” said Witters, the endocrinology professor. “[But] there are so many things that can affect performance that I would be very reluctant to tell someone, you can’t use this form or birth control, where it might be the best form of birth control.”

Even Randall, whose DVT experience was a major health scare, didn’t want to tell skiers to avoid birth control altogether. She just wanted them to be smart, and to be educated.

“I think [hormonal contraception] can be a really good thing,” Randall told FasterSkier. “It shouldn’t be something that everyone shies away from. But whenever you’re talking to your doctor, make sure that you’re really emphasizing that you’re an athlete and you’re a special case.”

As the cases of Yaz and NuvaRing illustrated, drug companies aren’t always honest about the side effects associated with their products. It’s important for skiers – like all women – to try to learn as much as they can about birth control before getting a prescription.

“I believe that drug companies have so much of an effect on the perception of birth control that its side effects are ignored,” one college racer said in FasterSkier’s survey.

Randall agreed.

“As an athlete I had to look at drugs with a hint of caution anyway to stay within the guidelines of the World Anti-Doping Agency,” she said. “So I felt like I had pretty good control over what was going in my body, but this was just such a casual thing. It was like, ‘yeah, this is what you do,’ so it really just caught me by surprise.”

There are, of course, other birth control methods. Belle*, a senior racer, had a suggestion for other women.

“Many forms of birth control don’t come in the form of oral contraception,” she wrote to FasterSkier in an e-mail when she learned about this piece.

“I used to take [birth control pills] until a non-skiing friend urged me to try an intrauterine device (IUD). IUD’s are one of the safest, most fool-proof forms of contraception, and especially for someone that travels and keeps a funny schedule, you don’t have to remember to take a pill at the same time every day. When I switched from the pill to an IUD, I had significant weight loss, which is important for skiing.”

Belle didn’t go so far as to say that using an IUD instead of hormonal contraceptives had made her a better skier, because she knew that many other things had changed in her life over that long period of time. But based on her own experience, she suggested that other athletes might want to think outside the pillbox.

For some athletes, hormonal contraception will never create problems in their performance, and Karlson, the doctor, said she thinks that women shouldn’t worry too much. If they start to believe that birth control pills are affecting them, it will, she said.

“For that person, they believe that it’s real, and you’re never going to change their mind,” she told FasterSkier.

But it’s important for skiers to know that if their performance starts to “go downhill,” as Joe had said, birth control might be one factor to consider. For those whose natural hormone profiles don’t play well with the pill, education is essential.

One thing is for sure: while hormonal birth control has wreaked havoc on a number of skiers, it’s made their later successes even sweeter. Like Egan’s.

“I actually had a job lined up as of February 2010, my senior year of college,” she told FasterSkier. “But in March, when I completely out-of-the blue qualified for NCAA’s, I began to think that continuing to ski might be a possibility. And only after that spring track season did I get offered the running scholarship that allowed me to go to UNH as a graduate student and athlete.

“I told my UNH teammates this year that whenever they are having a tough day at practice, and they feel that the last thing they are doing is ‘living the dream’ – they are living mine!”

After her DVT scare, Randall had a similar outlook on life.

“I think I take for granted that I have a pretty healthy body that can do just about anything, so it made me step back and think about just how lucky I am,” she said.


Chelsea Little

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  • Marjot

    August 17, 2011 at 10:48 am

    Thank you so much. Is there permission to share? Many older female athletes have been aware of these issues for years, yet, there is never any certainty that the “experts” know any more than the drug companies tell them…. Many early female marathon runers experienced the same performance decline issues from hormones. Unfortunately, some post menopausal women get enormous gains from Estratest (mix of testosterone and estrogen) and masters athletes are not drug tested. So be skeptical of these 50 somethings running very well!

  • SaraS

    August 18, 2011 at 11:28 am

    Thanks for this great article and research! I would agree with the ending thoughts – as female athletes we need to be there for each other in situations like this. Ask your teammates and coaches as well as doctors about these issues. We need to establish dialogue in these areas if we are to excel and make informed choices. Don’t be afraid to ask…we all deal with this stuff and should be able to discuss it within our teams without embarrassment!

  • Tim Kelley

    August 18, 2011 at 1:56 pm

    It seems like in the big picture of health for athletes that anecdotal evidence, experience from peers and common sense should be give as much or more credibility than research and studies. As Witters says: “research is [often] crappy”. And research can also be tarnished by profit motives and defense claims for personal opinions.

    A classic example of “research” being totally biased, and negatively affecting many athletes, occurred in the 1970’s. Back then airlines allowed smoking in the first 10 rows of coach class on airplanes. Everyone knew that second hand smoke was bad for you and the air in the plane was constantly being re-circulated. But airlines staunchly defended allowing in-flight smoking because “research from doctors has proven” that there was no risk to your health if you are sitting in row 11 behind chain smokers in row 10. Bottom line: the term “research by doctors has proven” … can often mean nothing.

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