Monitoring during gonadotrophin-releasing hormone antagonist protocols

The results of the four large industry sponsored multicentre clinical trials comparing gonadotrophin-releasing hormone (GnRH) antagonists and agonists in controlled cycles of assisted reproduction are reviewed from the perspective of implications for monitoring ovarian responses. The simplicity and consistency of antagonist-controlled cycles in normal women indicate that patients in assisted reproduction programmes should undergo fewer assessments and will receive shorter treatment cycles. However, the two-stage pattern of follicular recruitment in antagonist-controlled cycles leads to follicles of different size profiles at the end of the follicular phase compared with those obtained in agonist-controlled cycles (one recruitment process only). Increasing the dose of follicle-stimulating hormone (FSH) may increase oocyte yield, but does not obviate the difference between the two types of cycle. This difference has implications for the criteria used to determine timing of administration of the luteinization signal before oocyte retrieval.