In the context of assisted reproduction techniques, luteal phase support (LPS) describes the administration of medication aimed at supporting the implantation process. Luteal phase insufficiency is usually due to inadequate postovulatory progesterone production. Despite the rapid recovery of the pituitary function in gonadotropin-releasing hormone (GnRH) antagonist protocols, luteal phase supplementation remains mandatory. Progesterone induces a secretory transformation of the endometrium in the luteal phase. The intravaginal route of progesterone supplementation in in vitro fertilization (IVF) has gained wide application as a first-choice luteal support regimen, mainly due to patient comfort and effectiveness. Human chorionic gonadotropin (hCG) is an indirect form of luteal support by stimulating the corpora lutea. It raises E2 and progesterone concentrations, thus rescuing the failing corpora lutea in stimulated IVF cycles. The currently available evidence suggests that the addition of estrogen to progesterone for luteal phase support does not increase the probability of pregnancy in IVF.