When infertility is due to failure of an egg to grow (anovulation) fertility drugs are used to stimulate growth. When the egg reaches maturity, as judged by ultrasound, its release (ovulation) is often prompted by use of an ovulation trigger in the belief that it may help in timing intercourse, thus leading to better pregnancy rates. This review included two small, good quality trials evaluating the use of urinary hCG as an ovulation trigger (in normal intercourse cycles), in women receiving clomiphene citrate as an ovulatory agent. The combined results do not support the routine use of ovulation triggers, but we are unable to refute the value of this practice as the trials and participants were few in number. Trials involving other ovulation triggers and other fertility drugs were not available. More research in this area is required.
George, K.; Nair, R.; Tharyan, P. Ovulation triggers in anovulatory women undergoing ovulation induction. Cochrane Database of Systematic Reviews (2008) (Issue 3) Art. No.: CD006900. [DOI: 10.1002/14651858.CD006900.pub2]