**11. Chapter summary**

In contemporary ART, luteal phase progesterone supplementation is common practice. Various routes of administration have been developed, but most have proved to have limitations and some side effects. The use of oral progesterone is clearly inferior to intramuscular or vaginal administration and is associated with an increased rate of side effects due to its metabolites. While intramuscular delivery of progesterone continues to remain an option, an increasing number of fertility specialists prefer the vaginal route of delivery. At present, there are insufficient data for a direct comparison between intramuscular and vaginal progesterone therapy; therefore, physicians should be guided by their own clinical experience. Progesterone by whatever route or form can be started on ovum pickup day or within 48 hours, without significant differences in cycle outcome.

Luteal phase support with hCG is not superior to luteal phase support with progesterone. Supplementary administration of hCG brings no advantage when progesterone is administered . Luteal phase support with hCG increases the risk of OHSS as compared with progesterone. As yet, the role of estrogen supplementation therapy during the luteal phase of IVF cycles lacks enough evidence to be employed in routine practice. Combined luteal support using progesterone and GnRh-a showed benefit from addition of GnRH- a to progesterone for the outcomes of live birth, clinical pregnancy and ongoing pregnancy.
