Individualized luteal phase support after fresh embryo transfer: unanswered questions, a review

Background Luteal phase support (LPS) is an important part of assisted reproductive technology (ART), and adequate LPS is crucial for embryo implantation. At present, a great number of studies have put emphasis on an individualized approach to controlled ovarian stimulation (COS) and endometrium preparation of frozen- thawed embryo transfer (FET); However, not much attention has been devoted to the luteal phase and almost all ART cycles used similar LPS protocol bases on experience. Main body This review aims to concisely summarize individualized LPS protocols in fresh embryo transfer cycles with hCG trigger or GnRH-a trigger. The PubMed and Google Scholar databases were searched using the keywords: (luteal phase support or LPS) AND (assisted reproductive technology or ART or in vitro fertilization or IVF). We performed comprehensive literature searches in the English language describing the luteal phase support after ART, since 1978 and ending in May 2019. Recent studies have shown that many modified LPS programs were used in ART cycle. In the cycle using hCG for final oocyte maturation, the progesterone with or without low dose of hCG may be adequate to maintain pregnancy. In the cycle using GnRH-a for trigger, individualized low dose of hCG administration with or without progesterone was suggested. The optimal timing to start the LPS would be between 24 and 72 h after oocyte retrieval and should last at least until the pregnancy test is positive. Addition of E-2 and the routes of progesterone administration bring no beneficial effect on the outcomes after ART. Conclusions Individualized LPS should be applied, according to the treatment protocol, the patients' specific characteristics, and desires. Plain language summary Luteal phase support (LPS) is an important part of assisted reproductive technology (ART). In the cycle using hCG for final oocyte maturation, the progesterone with or without low dose of hCG may be adequate to maintain pregnancy. In the cycle using GnRH-a for trigger, individualized low dose of hCG administration with or without progesterone was suggested. The optimal timing to start the LPS would be between 24 and 72 h after oocyte retrieval and should last at least until the pregnancy test is positive. Addition of E-2 and the routes of progesterone administration bring no beneficial effect on the outcomes after ART. Individualized LPS should be applied, according to the treatment protocol, the patients' specific characteristics, and desires.

Automated summary

Luteal phase support (LPS) is crucial for embryo implantation in assisted reproductive technology (ART). Recent studies have shown the importance of individualized LPS protocols in fresh embryo transfer cycles, depending on whether hCG or GnRH-a trigger is used. The optimal timing for starting LPS and the combination with progesterone or hCG varies based on different trigger methods.