The luteal phase after 3 decades of IVF: what do we know?

The luteal phases of all stimulated IVF cycles are abnormal. The main cause of the luteal phase defect (LPD) observed in stimulated IVF cycles is related to the multifollicular development achieved during ovarian stimulation. This may be related to the supra-physiological concentrations of steroids secreted by a high number of corpora lutea during the early luteal phase, which directly inhibit LH release via negative feedback actions at the hypothalamic–pituary axis level, rather than a central pituitary cause or steroidogenic abnormality in the corpus luteum. To correct the LPD in stimulated IVF cycles, human chorionic gonadotrophin (HCG) or progesterone can be administered. HCG is associated with a greater risk of ovarian hyperstimulation syndrome. Natural micronized progesterone is not efficient if taken orally. Vaginal and intramuscular progesterone do have comparable implantation, clinical pregnancy and delivery rates. However, because of severe side effects, intramuscular progesterone administration should be avoided.