The Fertility Workout: Getting the Right Amount

Too little isn’t good for your health, but women have long been told that too much isn’t good for their fertility. Just how much exercise is the right amount to conceive?

Laura Flynn McCarthy, a New Hampshire-based freelance writer, had always been physically active, jogging and walking year round. So years ago when she and her husband decided it was time to start a family, she didn’t really change her exercise schedule. Today McCarthy—now the mother of two sons, age 17 and 10—is still an avid walker.

Turns out, she’s been doing just what more and more doctors “order” for their patients’ health, and for their patients’ children. In fact, a new wave of scientific research suggests that regular moderate exercise can even boost some women’s chances of getting and staying pregnant. Exercise can lessen the likelihood of high blood pressure and glucose metabolism problems that often interfere with fertility, as well as making it less likely during pregnancy that complications such as preeclampsia and musculoskeletal aches and pains will occur.

And the moment to start working out, wherever you are in your baby-planning agenda, is now.

At a time when only roughly 15 percent of women in their peak childbearing years are truly regular exercisers, “the desire to have a healthy child could be the perfect motivation to embark on a more healthful lifestyle, out of a feeling of duty and responsibility to a future family,” says Raul Artal, M.D., professor and chairman, department of obstetrics, gynecology, and women’s health, St. Louis University School of Medicine.

How Exercise Helps

It’s no secret that diabetes rates are rising at an alarming pace throughout the world, and that women who knowingly (or, often, unknowingly) have diabetes can experience problems getting or staying pregnant. In addition, gestational diabetes mellitus (GDM) is the single most common medical complication of pregnancy, affecting up to 6 percent of pregnant American women, and contributing to significant numbers of miscarriages, premature births, and maternal deaths every year. What’s not so well known: Moderate aerobic exercise could be one of the most potent means of prevention.

“There is now scientific evidence that exercise’s positive effect on body weight, body chemistry, and insulin resistance lowers diabetes risk,” says James M. Pivarnik, Ph.D., of the Center for Physical Activity and Health at Michigan State University, who chaired a scientific roundtable convened by the American College of Sports Medicine (ACSM) on “The Impact of Physical Activity During Pregnancy and Postpartum on Chronic Disease Risk.” In a consensus statement published just last year, the ACSM reported that studies of women who engaged in recreational physical activity showed that those who were most active one year prior to pregnancy had a 51 percent reduction in gestational diabetes risk. Continuing to be active during the first 20 weeks of pregnancy slashed the women’s diabetes risk even further, by 60 percent.

Being active, science has shown, can also affect a whole host of other body systems. Exercise is now part of more and more physicians’ prescriptions for those suffering from high blood pressure, which can also decrease fertility in women and men. Exercise, of course, can also help women lose excess weight that can hamper fertility.

Exercise can also help women manage conditions such as endometriosis, which can decrease the chance of pregnancy and cause persistent pelvic floor pain. “Being physically active can be a powerful antidote to physical and emotional pain,” notes Sheila A. Dugan, M.D., assistant professor of physical medicine and rehabilitation medicine at Rush University Medical Center in Chicago. “We may not have identified the specific metabolic pathways involved, but there’s no question that engaging in physical activity benefits a woman’s overall health.”

Among exercise’s other positive impacts reported by the ACSM and American College of Obstetrics and Gynecology (ACOG): prevention of excessive weight gain that could put a pregnant mother and developing baby at risk; improved energy levels during pregnancy; greater strength and endurance (especially important since for some women, notably those over 40, pregnancy can be “equivalent to a nine-month marathon,” as one doc put it); and, possibly, less risk of preterm delivery or under- or overweight newborns; and faster delivery and recovery from childbirth.

How Much is Too Much?

While one of the benefits of physical activity is undoubtedly weight control, there’s also the question of whether a woman can overexercise to the point of excessive weight loss, eventually compromising her fertility. The latest scientific conclusion: “The infertility problem in exercising women is not that they are exercising too much. The problem is that they are eating too little,” claims Anne Loucks, Ph.D., professor of physiology at Ohio University in Athens. Loucks’ groundbreaking studies have shown that low energy availability—not too much exercise or too little body fat—causes some women who exercise regularly, but do not replace enough of the calories they burn, to develop imperceptible menstrual disorders such as luteal phase deficiency or low ovarian function.

“If there isn’t enough energy from food available to meet all of the body’s needs, it may prioritize how it uses its energy. And the reproductive system may be low on the list,” Loucks explains. Her research suggests that LH pulsatility, which is necessary for fertility, is thrown off in low energy availability in exercising women. “We used to think it was the effect of how much body fat a woman had, but a whole range of researchers have found that amenorrheic athletes don’t necessarily have less body fat than regularly menstruating athletes, but they do have less dietary energy remaining after exercise for all the physiological processes that occur in their fat-free mass.”