Obstetric, Neonatal, and Clinical Outcomes of Day 6 vs. Day 5 Vitrified-Warmed Blastocyst Transfers: Retrospective Cohort Study With Propensity Score Matching

Abstract

Despite the large number of studies on blastocyst transfers, it is unclear whether day 6 blastocysts have similar pregnancy rates and safety with day 5 blastocysts. Thus, this study aimed to compare the obstetric, neonatal, and clinical outcomes of day 5 and day 6 vitrified blastocyst transfers (VBT). In this retrospective cohort study with propensity score matching, we evaluated 1,313 cycles of VBT performed between January 2014 and December 2015 at the Fertility Center of CHA Gangnam Medical Center. All cycles underwent natural endometrial preparation. We used propensity score matching to compare day 5 and day 6 VBTs in a matched comparison. After propensity score matching, there were 465 cycles of day 5 VBT and 155 cycles of day 6 VBT. Implantation rate (IR), clinical pregnancy rate (CPR), and live birth rate (LBR) were significantly lower in day 6 VBTs (44.2 vs. 53.1%, p = 0.023; 48.4 vs. 60.4%, p = 0.009; 33.5 vs. 51.8%, p < 0.001). Miscarriage rate was significantly higher in day 6 VBTs (29.3 vs. 10.7%, p < 0.001). Rate of multiple gestations was similar between the two groups (29.3 vs. 30.2%, p = 0.816). Assessing 241 and 52 babies from day 5 and day 6 VBTs, no differences were found in neonatal outcomes including rates of low birth weight, preterm birth, and congenital malformations. In propensity score-matched analysis, obstetric, and neonatal outcomes between day 5 and day 6 VBTs were similar so that day 6 VBTs are as safe as day 5 VBTs. IR, CPR, and LBR were are all significantly lower in day 6 VBTs. Therefore, if there are no differences in the morphological grade between day 5 and day 6 blastocysts, transfer of day 5 vitrified blastocysts should be considered first.

Analysis of Biochemical and Clinical Pregnancy Loss Between Frozen-Thawed Embryo Transfer of Blastocysts and Day 3 Cleavage Embryos in Young Women: A Comprehensive Comparison

“…In the present study, we found that Group B and FET cycles with Day 6 blastocysts had a significantly higher rate of CPL than Group A and FET cycles with Day 5 blastocysts, respectively. Part of these results was consistent with previous reports that transfer of Day 6 blastocysts resulted in a significantly higher miscarriage rate than that of Day 5 blastocysts (43,44). These results indicated that MA or days of blastocyst could serve as an independent factor affecting the occurrence of CPL.…”

Live birth rate following frozen-thawed blastocyst transfer is higher in high-grade day 6 blastocysts than in low-grade day 5 blastocysts

“…In our study, no difference was observed between four groups in terms of preterm birth rate, very preterm birth rate, and live birth weight of newborns. Our results are in line with a propensity score-matched analysis ( 24 ), in which the obstetric and neonatal outcomes between D5 and D6 vitrified blastocyst transfers were similar. Some studies indicated that delayed blastocyst expansion (D6 vs. D5) is prone to achieve heavier newborns than D5 blastocysts due to the extended culture in vitro ( 25 ).…”

Increased incidence of live births in implanted single-embryo transfer cycles of vitrified-warmed blastocysts expanded on day 5 versus day 6 following preimplantation genetic testing for aneuploidy

“…1). Generally, delayed blastocyst development is associated with an increased risk of mosaicism [26], indicating that the incidence of aberrant ploidy in D6 blastocysts may increase and thereby lead to an increased risk of FL in non-PGT-A cycles [33][34][35]. However, according to our ndings, the difference in ploidy status between the D5 and D6 blastocysts may not be the only intrinsic factor in uencing the postimplantation development of embryos.…”