Chronic anovulation is a very common disorder in polycystic ovary syndrome (PCOS) patients wishing to conceive. In these patients, ovulation induction resulting in restoration of a regular menstrual cycle with monofollicular ovulation may normalize the probability of pregnancy. This may be achieved either by increasing the follicle-stimulating hormone (FSH) serum concentration or by improving the endocrine ovarian milieu resulting in enhanced FSH responsiveness of the ovaries. Later on, this favorable endocrine milieu may also benefit implantation, embryo development and reduce risks in pregnancy for mother and child. A combination of both strategies could be used to individualize treatment in a patient-tailored way: for every patient an optimal effective treatment plan based on specific individual characteristics. Although there has been a tendency to ultimately skip ovulation induction and start in vitro fertilization (IVF) immediately because this would result in better pregnancy chances, this choice neglects the significant risks and physical burden of IVF treatment and significant higher costs. Ovulation induction in PCOS patients, as discussed in this chapter, is a very successful treatment option with a cumulative single live birth of greater than 70% during a 24-month follow-up period.

The lack of ovulatory cycles may be considered as a major problem for women seeking pregnancy. This is reflected by the fact that about 20 percent of couples visiting a fertility clinic with an unfulfilled wish to conceive present with anovulation [1]. Clinical manifestation of anovulation is oligomenorrhea (intermenstrual period > 35 days) or amenorrhea (intermenstrual period > 6 months). Although ovulation may occur in oligomenorrhea, the longer the time period between menstruations the smaller the chance of that cycle being ovulatory. Classification of anovulatory patients may be performed using the criteria of the World Health Organization (WHO) as determined by Rowe et al.