Anovulation is the term used to describe a situation in which a woman does not ovulate; that is, she does not release any eggs. Anovulation can in general be avoided and can typically be corrected.
Breastfeeding, excessive weight change (either gain or loss), illness, quitting birth control, stress and strenuous exercise can all cause anovulation. Pituitary and thyroid problems, as well as PCOS (polycystic ovarian syndrome) can cause anovulation as well.
There are several things that a physician can do to help overcome anovulation. There are several drugs such as Clomid and Pergonal that can increase your chances of ovulating. These fertility drugs can greatly increase your chances of having multiple pregnancies.
There may also be herbs that can help with helping to induce ovulation. Vitex, also known as chastetree berry is one of the most popular. Dong Quai is another herb that purports to regulate hormones, which would also help with ovulation. Evening Primrose Oil helps with producing fertile quality cervical fluid and vitamin B6 helps to lengthen the luteal phase (the time from ovulation to menstruation).