Exercise Hinders Pregnancy for Women Using IVF

Women trying to conceive using in vitro fertilization (IVF) are less likely to conceive if they regularly exercise four or more hours per week, according to a recently released study.

In general, the study found that regular exercise did not seem to decrease or increase a woman's chance of having a baby through IVF. However, the odds of a live birth for women who exercised four or more hours per week fell 40 percent compared to women who didn't exercise. The ninie-year study evaluated more than 2,000 women who tried to conceive via IVF.

Dr. Ina Cholst, an associate professor of obstetrics and gynecology at Cornell University's medical college, told "Good Morning America Weekend Edition" that the study's results may have biological roots dating back to cave men,

"One way to think about it is that way back in the caveman days when we were running from the wild animals, starving, stressed as a population, there wasn't such a good time for people to get pregnant," Cholst said. "Nature's kind of built in a defense mechanism so that when there's a lot of exercise or other kinds of stress, pregnancy doesn't occur so easily."

If you're trying to conceive, don't over-exercise, Cholst said.

"If you were trying to get pregnant and you were exercising very vigorously and your period stopped, that would be a time to cut back, that's for sure," she said.

Young women who are trying to get pregnant naturally, however, shouldn't stop exercising altogether, Cholst said.

"If they're young and they've been exercising and they're fit, they ought to do exactly what they've been doing," she said. "On the other hand, if people are at an age where fertility may be an issue, there's a smaller window in which they ... can conceive, then they probably should be a little bit more moderate and sensible about it."