The Natural Cycle for In Vitro Fertilization: A French Experience

Abstract

The use of the natural cycle for in vitro fertilization (IVF) began in our institution at the end of 1987. A simplified protocol was developed based upon an understanding of the physiology of the menstrual cycle. Three major points are of particular importance. The first point is the realization that the final stages of oocyte maturation are initiated by the luteinizing hormone (LH) surge and are achieved just prior to ovulation.1,2 Second, spontaneous ovulation occurs between 35 and 42 hours after the onset of the LH surge. Therefore, if the endogenous LH surge is to be used for timing oocyte retrieval, it is necessary to detect its onset. The several LH determinations that are necessary to detect the LH surge are not compatible with laboratory scheduling in most IVF centers. Therefore, to avoid multiple daily measurements of LH we prefer to trigger ovulation with an injection of human chorionic gonadotropin (HCG) before the spontaneous LH surge occurs.