Modified Luteal Support for Frozen-Thawed Embryo Transfer - A Prospective Study

Background With the recent trend toward single embryo transfer (ET) adopted in an attempt to reduce the risk of multiple pregnancy, the remaining extra embryos are cryopreserved, providing further possibilities for conception after the initial fresh transfer. Moreover, several studies that compared fresh and frozen-thawed embryo transfer (FET) cycles in normal responders have demonstrated a significantly higher clinical pregnancy rate per transfer in the FET versus the fresh cycles.

There are several currently employed replacement protocols for FET. The choice of protocol depends on the individual woman's ovarian function and convenience of the method, as well as on the experience gained with the method by the physicians. Whatever protocol is used, the success requires optimal synchronization between the embryonic stage at thawing and date of the endometrium within the endometrial preparation cycle. While there is a consensus regarding the duration, route of delivery and dosage of estrogen supplementation, and the optimal ultrasonographic endometrial appearance and thickness, the effect of the different modes of luteal support remains unclear.

Prompted by the study demonstrating higher ongoing pregnancy rate following the transfer of frozen-thawed embryos in natural cycles with spontaneous LH rise compared with natural cycles controlled by hCG for final oocyte maturation and the reports showing improved pregnancy rate in patients who received a mid-luteal injection of a GnRH-agonist (0.1 mg triptorelin), the investigators started beginning at June 2014 to offer ovulatory patients with regular menstrual cycles a natural FET with modified luteal support. Starting on the day of spontaneous ovulation, patients received daily vaginal progesterone, supplemented by a single injection of HCG and GnRH-agonist, on day of ET and 4 days later, respectively.

The results for this study were very promising - the investigators were able to show a significant increase in implantation rate (30% vs. 17%; p<0.03), clinical pregnancy (48% vs. 26%; p<0.01) and ongoing pregnancy (39% vs. 20%; p<0.01) for the patients receiving the aforementioned modified luteal support protocol.

After the completion of this retrospective study the investigators are heading to prove the superiority of the modified luteal support protocol for ovulatory patients by conducting a prospective study.