How Exercise Affects Fertility

Fit & Healthy Pregnancy is a friendly, comprehensive guide to exercising before, during, and after pregnancy from athlete-moms, Dr. Kristina Pinto and Rachel Kramer, MD.

Of course you won’t exercise while pregnant until you first get pregnant! Athletic women can have particular concerns about conception and fertility because the reproductive system responds to how much energy we expend by working out. We’re not talking about how you get through a triathlon during your period or the nuances of core work with severe menstrual cramps. And we’re not talking about the tricky business of using up so much energy at the gym that you have zero interest in sex.

Yes, conception is closely tied to energy, to the extent that your body needs enough nutrition, particularly fat, to compensate for your activity and stay in a healthy zone for conceiving and supporting the growth of a fetus. But while exercise intensity and volume are often held responsible for how easily an athletic woman conceives, there are several factors in menstrual regularity that can play out in fertility issues including: balance of energy use and fuel intake (calories), body weight and composition, disordered eating habits, psychological stress, and all of this varies among each individual.

cycling, cyclist, endurance sports, exercise, exercise and fertility, fit pregnancy, fit and healthy pregnancyWhen you have missing, infrequent, or irregular periods as a result of any of those factors, you might experience trouble conceiving, which is known as ovulatory infertility. It’s like trying to make an omelet without eggs. Although working out is something of a scapegoat, exercise at high levels of training volume, particularly in endurance sports, can change the frequency and regularity of menstruation, making it hard to predict your ovulation. For example, one study of distance runners found that an increase in mileage from 30 to 42 miles per week was associated with the rate of amenorrhea (missing a period for at least 3 months in a row) going from 2 percent to 31 percent.

The thing is, statistics like this can create the false belief that exercise causes ovulatory infertility, which isn’t the case. Amenorrhea associated with exercise has to do with food intake and energy use and maintaining the balance between them. Exercise simply affects that balance, which wobbles when a woman isn’t getting enough calories from fat to support her energy use. The result is a disruption in the hormones that direct her ability to conceive and may change her body mass index (BMI), which influences menstrual regularity.

For more on BMI and getting pregnant, check out our other articles: Exercise BMI and Getting Pregnant and More on Exercise, BMI, and Getting Pregnant.

Please consult your doctor before embarking on an exercise program during pregnancy.

Fit & Healthy Pregnancy dispels generations of old wives’ tales about exercise and pregnancy. Exercise during pregnancy isn’t just safe, it’s healthy for you and your baby. This modern, comprehensive guide shows active women how to stay strong and in shape before, during, and after pregnancy.