Exercise as a risk factor for infertility with ovulatory dysfunction.

To examine the relation of regular vigorous exercise to ovulatory infertility, we interviewed 346 infertile women, in whom there was evidence of ovulatory failure, regarding their exercise patterns during the year preceding their unsuccessful effort to conceive. Their responses were compared with similar exercise histories in women who had successfully conceived at the time the infertile women started trying to become pregnant. Vigorous exercise for an hour or more per day was reported more commonly in nulligravid cases (n = 187) than by their primiparous controls. The difference was particularly great in the subgroup of cases without additional evidence of tubal dysfunction (relative risk = 6.2, 90% confidence interval = 1.0 - 39.8). This association was not seen among infertile women who had previously been pregnant. Vigorous exercise for an average of less than one hour per day was not associated with either primary or secondary infertility.