Unexpected pregnancies exposed to leuprolide acetate administered after the mid-luteal phase for ovarian stimulation

Leuprolide acetate (Lupron) belongs to the group of gonadotrophin-releasing hormone agonists (GnRHa). It is used in conjunction with human menopausal gonadotrophin (HMG) and/or follicle stimulating hormone (FSH) for ovarian stimulation in the so-called ultra-short, short or long protocols. In our programme, the long protocol is mainly used, which starts routinely with s.c. administration of Lupron, 1 mg/day, from day 21 of the cycle preceding ovum retrieval. After pituitary desensitization is achieved, gonadotrophin administration is started. However, unexpected, spontaneous pregnancy may occur during the flare-up phase of Lupron administration. We present six pregnancies and four deliveries which have occurred under these circumstances. The mechanisms by which pregnancy may occur and escape from luteolytic, abortifacient and teratogenic effects of prolonged use of GnRHa are discussed, as well as pregnancy outcome.