#198 : When to Transfer Day 6 Vitrified Embryos? On Day 5 vs Day 6 of Progesterone, a Retrospective Analysis

Abstract

Background and Aims: The age of cryopreserved embryos impacts the ART outcome of frozen embryo transfer cycles. The development potential of embryos is not uniform. Though the days of progesterone exposure before transfer of D5 blastocyst is so far standardized, there is lack of standardization on transfer of Slow growing embryo i.e. D6 blastocysts. So, this study aims to compare the clinical outcomes of D6 blastocyst transferred on the 5th day or 6th day of progesterone supplementation. Method: The retrospective data were collected from the central registry of Indira IVF Hospital Private Limited to analyze 62227 frozen cycles from April 2019 to July 2021, divided into two groups: D6-Frozen embryos transferred on P+5 (Group A) vs P+6 (Group B). Results: There were 1212 cycles in Group A, and 189 cycles in the Group B arm in the final analysis). The propensity scores were calculated using binary logistic regression and the nearest neighborhood technique based on the following variables at baseline: Wife Age, Husband Age, Body max Index (BMI), Anti mullerian hormone (AMH), and Endometrial thickness. The clinical pregnancy rate was significantly higher in Group A than in Group B (CPR 70.5% vs. 63.0%, p=0.037). No significant differences were observed in the biochemical pregnancy rate (72.6% vs. 66.1%; p=0.066), biochemical loss rate (3.0% vs. 4.8%; p=0.271), clinical miscarriage rate (15.9% vs. 13.4%; p=0.485), live birth rate (59.2% vs. 54.5%; p=0.218) and multiple live birth rate (16.5% vs. 14.8%; p=0.559). Conclusion: In this study Frozen Embryo Transfer of D-6 blastocysts on the day-5 of progesterone results in better pregnancy outcomes than the day-6 of progesterone.