Concealed ovulation decreases paternity certainty because men are unsure when women ovulate. Danielle was also placed on Clomid to help her produce eggs and ovulate regularly. Sometimes follicular dominance is manipulated to allow more follicles to ovulate. He is credited with showing in 1905 that women only ovulate once per menstrual cycle. In alpaca, follicles ovulate approximately 26 hours after coital stimulation. After their offspring are weaned, females begin to ovulate and soon become pregnant again. A female can become pregnant through sexual intercourse after she has begun to ovulate. Another major cause of infertility in women may be the inability to ovulate. A female can become pregnant from sexual intercourse after she has begun to ovulate. Wildebeest females breed seasonally and ovulate spontaneously. Furthermore, while lactating, females do not ovulate and consequently are not fertile. Mothers may not ovulate, or have regular periods, during the entire lactation period. A minority of females four to five months old ovulate and a few become pregnant. The length of time in which a postpartum woman does not ovulate is another factor. If the females are nursing infants, it's likely that they won't ovulate for another year.