Effect of repeated administration of clomiphene citrate at two different times on the endometrium in patients undergoing intrauterine insemination.

Clomiphene citrate (CC) has been widely used for induction of ovulation; however, despite the high rate of ovulation, the pregnancy rate is only 30%. The anti-estrogenic effect of CC on the endometrium is one explanation for this finding. It is well known that repeated administration of CC enhances its anti-estrogenic effect. To overcome this adverse affect, a number of techniques have been used. One technique is the early administration of CC, in an attempt to decrease the anti-estrogenic effects of CC on the endometrium. The aim of the present study was to retrospectively evaluate if repeated administration of CC at varying times may affect the endometrium during preovulatory period; pregnancy rates were compiled for patients with unexplained infertility undergoing intrauterine insemination (IUI). The patients were divided into four groups based on the number of repeat administrations and the time of CC administration. The endometrial thickness at the day of human chorionic gonadotropin administration was greater in early administration within three consecutive CC cycles than the others. When the endometrium is thin during classical administration of CC, it is worth attempting the early administration of CC in the CC/IUI treatment for patients with unexplained infertility. However, this effect disappeared over the duration of the three consecutive CC cycles. (Reprod Med Biol 2004; : 153-157).