Trying to Get Pregnant? What Runners Should Know.

What Runners Should Know About Trying to Get Pregnant

There aren’t specific mileage guidelines for women who want to get pregnant because every woman is different.

Deciding to start a family brings a lot of excitement…and a lot of questions. Is the timing right? Will everything work as it’s supposed to? Will the baby be healthy? Women are frequently reminded to consider their age when trying to get pregnant, but for many women runners, another number they worry about is their mileage.

“Every time I would run a hard workout, I would think to myself: am I harming my chances of getting pregnant by doing this?” says Jennifer Fox, a marathoner who was 27 when she first started trying to conceive. “There weren’t any good guidelines on what was the rule. Is 40km a week okay? 80 kilometres? I wasn’t sure.”

Assume Fertility, but Practice Patience

The reason for the lack of specific mileage guidelines is that every woman is different. Some get pregnant in the middle of marathon training; for others 30-kilometre weeks may be too much. But, to start with, “The number one recommendation is to assume you’re fertile unless proven otherwise,” says Alice Domar, director of the Domar Center at Boston IVF in the US and author of Conquering Infertility. “If you are a runner and you have regular menstrual cycles, I wouldn’t worry about changing your routine unless you can’t get pregnant,” which means a year of trying for women under 35. (Doctors agree age is a bigger issue than exercise habits or mileage. Because the chance of conceiving decreases with age, older women may have less time to spare. Women 35 to 40 should consult a doctor after trying for six months; for women over 40, it’s just three months.) Sarah Crane, an OB/GYN and professor at Boston University School of Medicine, says women are so used to micromanaging their fertility to not get pregnant that they expect to conceive right away, but it’s perfectly normal to take months.

An Irregular Red Flag

The exception is if you are not getting a regular period; abnormal menstrual cycles are a red flag. After stopping hormonal birth control, it can take three months for your cycle to right itself. If it is still abnormal after that, you may need to evaluate your running and eating habits. (For an 18- to 35-year-old, a normal cycle is between 22 and 33 days long.) “In order to get pregnant, your body has to believe that it’s a good time for you to build a baby… that you are in a relatively safe place with enough calories to support a pregnancy,” Domar says. Although underweight is defined by a BMI of 18.5, Crane says some women with BMIs at the lower end of normal (in the low 20s) may need to gain a few kilograms before they can conceive. (On the other hand, being obese is proven to decrease fertility. For women who are overweight and trying to conceive, there is no question: running is highly encouraged. In fact, for most of her patients trying to conceive, “The harder thing – in my practice, anyway – is getting people to exercise,” says Erin Dawson, an OB/GYN and runner.)

After a few months of trying, Fox admitted to her doctor that her menstrual cycles were abnormally long. She was told to cut back her running, despite having a normal BMI. “I was frustrated because that was a source of joy for me and that was hard; that’s something that I love to do,” says Fox. But she wasn’t ovulating and even fertility medications wouldn’t help.

Still, small changes can make a big difference. Dawson says, “Sometimes it’s just a few kilos of weight gain and just a small decrease in mileage and they’ll start cycling again.” After Fox gained just two-and-a-half kilograms, by changing her eating to ensure she was getting ample kilojoules and enough healthy fat, she was able to start ovulating with the help of the drugs.

The Other Half of the Equation

If you have regular periods and are unsuccessful after a few months of trying, there is still a chance running may be the culprit. Women who exercise have been shown to have lower progesterone levels in the luteal phase, the phase that follows ovulation and prepares the uterine lining for implantation, says Crane. “Even if your cycle appears to be relatively normal you can be affecting your ability to conceive and carry,” she says.

But that’s unlikely to be an issue, says Dawson. “For women who cycle regularly, I’d be reluctant to tell them to decrease their running.” She suggests using an ovulation predictor kit (available from pharmacies) to confirm you’re ovulating. If a couple has been trying for six months and the woman is ovulating, Dawson would first test for other issues. “I think it’s unlikely that the running is a cause.”

After all, there is another half to this equation: the man. Should he be concerned about his exercise habits? Sperm production can be affected by working out in hot conditions; bicycling may be particularly problematic because the seat traps the testicles against the body, overheating them. But if a woman is menstruating and the couple is struggling, it’s relatively easy to test the sperm.

How to Cope If Told to Reduce Running

For the majority of women, running won’t affect their ability to get pregnant so there’s no need to cut back. But it can be a tough time for goal-oriented, Type-A runners who do struggle to conceive and are told to dial back. “I think the hardest piece for me, with the whole trying to conceive and failing, was that I didn’t think I was doing anything well,” says Fox. “I wasn’t able to run well, I wasn’t able to conceive. I was in this weird limbo.” Cross training, yoga, or meditation may help with stress normally relieved by a long run.

Remember that it’s a temporary sacrifice, says Domar. “Focus on the fact that this is not forever.” Once pregnant, you’ll likely get the go-ahead to resume running, as exercise is recommended throughout pregnancy. You’ll have to listen to your body on a daily basis as it changes – and slows down – throughout pregnancy; every woman and every pregnancy is different, with some women running up until their delivery date and others stopping because it becomes too uncomfortable. But overwhelmingly, exercise during pregnancy is highly encouraged, even for those who had to cut back in order to conceive.

After trying for more than a year, Fox conceived with the help of fertility medications. She was then able to increase her mileage, complete half marathons mid-pregnancy, and continue running until 39 weeks. She now has two healthy children and is running faster than ever.


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