Delaying the initiation of progesterone supplementation results in decreased pregnancy rates after in vitro fertilization: a randomized, prospective study.

Objective: To compare IVF outcome between two protocols for luteal phase supplementation, one beginning on day 3 after oocyte retrieval and the other beginning on day 6 after retrieval.

Design: Prospective, randomized study.

Setting: University-based assisted reproductive technology center.