Women and physical activity: can high-level sport harm the fertility of athletes?

Olympic gold medalist Laura Kenny is the most successful female athlete in UK history.

The mother of two boys, she also suffered a miscarriage and experienced an ectopic pregnancy, and always wondered whether the physical weight of high-level sport had harmed her fertility.

Laura is 32 years old and has dedicated her body to cycling for over ten years.

“In every training session I gave 100%, in every race I gave 100%.”

If I didn’t get sick after a race, I would think to myself, “Did I try hard enough?” »

This absolute commitment bore fruit in the velodrome. Two gold medals at the London Olympics in 2012 were followed by two more in Rio in 2016.

She married fellow cycling phenom Jason Kenny at the end of that year and the couple had their first child, Albie, in 2017. She went on to win another gold medal and a silver medal at the Tokyo Olympic Games (held in 2021).

But she had a miscarriage in November 2021 and five months later, she suffered an ectopic pregnancy, that is to say the embryo implants outside the uterus, which requires emergency surgery.

“I went from having a lot of control over my body to having a lot of control over my body,” she told the BBC.

Laura had never worried about her fertility before. Albie’s conception was simple and the pregnancy went well.

But since she spoke publicly about losing her baby, other athletes have told her they experienced the same thing.

The question remains: can high-level sport have a negative impact on the fertility of female athletes?

“Could it be that my body was exhausted and reacted by saying ‘I can’t go on like this’?

End of Instagram post

Miscarriages are common. Around one in four pregnancies end before 24 weeks and many occur at a very early stage. Most couples never find out why.

But are top athletes more exposed to fertility problems?

Emma O’Donnell, a physiologist at Loughborough University, explains that a professional athlete’s lifestyle puts different demands on her body.

Elite training burns an extraordinary amount of calories, and as a result, athletes’ bodies are typically lean and muscular, with very little body fat.

If they don’t eat enough to keep up with the calories they burn, problems with menstrual cycles, such as being interrupted for months or even years, are “very common,” O’Donnell says.

Nearly two-thirds of female athletes have interrupted periods, especially in endurance sports. High percentages are also recorded among elite gymnasts, ballet dancers and figure skaters. In the general female population, the percentage of interrupted periods is between 2 and 5%.

The absence of periods can be a sign that ovulation (or the release of the egg) is not taking place.

“We’re not 100 percent sure,” O’Donnell says, but the main idea is that conceiving a baby is such an energy-intensive task that the brain shuts down the whole process. reproduction if he thinks the body does not have enough energy.

It starts with the hypothalamus, a small structure in the center of the brain that senses the body’s nutritional status.

Just below the hypothalamus is the body’s hormone factory, the pituitary gland.

Normally, this gland releases hormones that travel to the uterus and ovaries to control the menstrual cycle and egg production, making pregnancy possible.

But if the hypothalamus is not satisfied, this process is interrupted and ovulation does not occur.

“If you don’t ovulate, you can’t have a child. You can’t conceive because there’s no egg release,” says O’Donnell.

The main factor appears to be the large number of calories burned during exercise training, which can make it difficult for athletes to eat enough to compensate.

This phenomenon, known as relative energy deficit in sport (RED-S), was first recognized by the International Olympic Committee in 2014.

But it’s likely that other factors are also involved, says Professor Geeta Nargund, a consultant at St George’s Hospital and medical director of the charity Create Fertility.

Body fat contributes to the production of the sex hormone estrogen.

“If exercise affects body fat levels, it of course has an effect on estrogen levels,” she explains.

Psychological stress – potentially caused by the pressure of training and competition – can also disrupt the menstrual cycle.

“That’s what we see in women with high levels of anxiety,” says O’Donnell.

The interruption of menstruation and egg production is the most clearly recognized impact on an athlete’s fertility, but it should resolve when she retires from sport, she notes.

For athletes who manage to get pregnant, there are always risks. Once an egg has been fertilized, it should implant in the wall of the uterus. However, in the case of an ectopic pregnancy, the egg implants elsewhere, usually in the fallopian tubes that connect the ovaries to the uterus.

In the UK, around 11,000 pregnancies are ectopic each year. It’s not clear why they occur, although inflammation and scar tissue in the fallopian tubes can increase the risk.

“But in this case, I don’t see a direct link between sports and the increased incidence of ectopic pregnancies,” says Nargund, who has treated athletes with fertility problems.

However, she believes there may be a link between very strenuous exercise during the first three months of pregnancy and miscarriage, although more research is needed to be clear.

She cites a large Danish study that followed more than 90,000 women and suggested that the more intense the exercise, the higher the risk. This is especially true for heavy, high-impact exercises.

“If you’re at Laura Kenny’s level, elite athletes, you’re at the top,” Nargund says.

She explains, however, that the study results should be interpreted “with caution” because the way the study was designed indicates that there may be other explanations that were not considered.

Separately, a very small study of 34 Norwegian female athletes found no increased risk of fertility problems, including miscarriage.

“We need to do a lot more research on sports, exercise, hormonal balance and reproduction,” says Nargund.

Lauren Nicholls played high-level netball for 10 years, then had two children, before becoming coach of the Loughborough Lightning, a British team. She says today’s players’ conversations about fertility are different from those she had with her former colleagues.

“I know some slightly older players who have frozen eggs and put off the decision to start a family,” she says. “Because they are now worried about their careers.”

Reconciling the dream of being a top athlete and that of starting a family has always been a delicate challenge to overcome. For women, the years of peak fertility coincide with their physical peak.

Male athletes are also not immune to fertility issues.

Burning more energy than you consume can affect testosterone levels, cause sperm abnormalities and even erectile dysfunction.

But for Emma Pullen, a sports exercise researcher at Loughborough, the lack of definitive answers on the impact of high-performance sport is emblematic of the insufficient research on female athletes, whether on fertility or risk of injury.

She says research on women lags behind the attention science has given to men’s sports.

“We’re seeing the impact of that with the increasing professionalization of women’s sports and the increase in the number of female athletes,” says Pullen.

Overall, Nargund believes that female athletes probably face more fertility issues than other women.

“It appears there is a fertility problem due to the potential effect [du sport de haut niveau] on ovulation, including a potentially higher risk of miscarriage,” she says.

But it’s not clear how much high-level exercise is excessive. And that’s enough for Lady Laura for now.

“I think the conversation itself is very important because I want people to start talking,” says Laura. “Honestly, I would like the debate to be much more open.”

Either way, the relationship between exercise and fertility concerns us all, even if we are far from Olympic glory.

Most men and women benefit from exercising and losing excess weight before trying to conceive – this is known to increase fertility.

Regular physical activity reduces stress, improves sleep and makes periods more regular in people with polycystic ovarian syndrome (PCOS).

But amateur athletes who train intensely can also end up depleting their energy, interrupting their periods or making them irregular.

“It’s not exactly the same thing, but it happens,” says O’Donnell.

Ensuring the balance between energy intake and production is “very important for ovulatory cycles” and key to maintaining reproductive function, she adds.

“Amateur athletes are not aware of how many calories they need to take in to meet energy demands.