Association of the duration of post-thaw culture with clinical outcome after vitrified-warmed day 3 embryo transfer in 10,464 cycles: A retrospective cohort study

This study aimed to investigate the effect of the duration of embryo culture on clinical outcome in vitrified-warmed cycles.This retrospective cohort study enrolled 10,464 infertile patients, with a total of 18,843 vitrified-warmed day 3 embryos from 2012 to 2017 at a single center. The patients were divided into 2 groups: 9470 cycles in the short-term culture group (0.5-8 hours of post-thaw culture) and 994 cycles in the 48 to 72 hours culture group. The independent effect of the following variables on clinical outcomes was determined: duration of post-thaw culture, maternal age, transferred embryos, embryo quality, and endometrial thickness.We found that the pregnancy rate was positively associated with the post-thaw culture time. Ordinary least square regression analyses showed that the duration of post-thaw culture was positively associated with implantation and live birth rates overall. However, the implantation and live birth rates were not significantly associated with the post-thaw culture time in the short-term culture group. Additionally, maternal age and the number of transferred embryos were independent predictors of the implantation and live birth rates. Moreover, the duration of post-thaw culture did not affect live birth weight.These results indicated that the pregnancy rate is positively associated with the duration of post-thaw culture. Therefore, under the condition of not affecting work shifts, properly prolonging the duration of post-thaw culture to improve the outcome of frozen-thawed embryo transfer should be considered.

Effect of a prior cesarean delivery on pregnancy outcomes of frozen-thawed embryo transfer: A retrospective cohort study in a freeze-all setting

INTRODUCTION

The association between the mode of previous delivery and subsequent success of assisted reproductive treatment has been poorly understood. By mitigating the detrimental effect of supraphysiologic estradiol levels on endometrial receptivity, a freeze-all strategy provides a novel model to investigate the sole impact of a prior cesarean delivery (CD) on embryo transfer outcomes.

MATERIAL AND METHODS

This single-center retrospective cohort study included 2660 patients who underwent their first frozen-thawed embryo transfer cycles after a freeze-all policy from January 2013 to December 2018. Patients with a history of live birth by CD were assigned to the CD group, and those with only vaginal delivery (VD) were categorized into the VD group. The primary outcome measure was live birth. Baseline characteristics of the two groups were balanced by propensity score matching in a ratio of 1:1. Univariate and multivariate logistic regression analyses were performed using the after-matching data.

RESULTS

Compared with the VD group, the rates of clinical pregnancy (38.3% vs 44.5%; P = .005) and live birth (27.5% vs 33.4%; P = .003) were significantly lower in women with a history of CD. When adjusted for a number of major confounding factors, the negative association between a prior CD and frozen-thawed embryo transfer success was maintained, with the adjusted odds ratio (OR) being 0.80 (95% CI 0.66-0.96) and 0.78 (95% CI 0.63-0.95) for clinical pregnancy and live birth, respectively. Furthermore, a CD history conferred a marginally increased risk of early miscarriage (crude OR 1.48, 95% CI 1.04-2.11; adjusted OR 1.47, 95% CI 1.01-2.14), whereas the odds of multiple and ectopic pregnancy did not show significant differences before and after adjustment.

CONCLUSIONS

A prior CD was associated with a decreased chance of live birth and an increased risk of early miscarriage in frozen-thawed embryo transfer cycles.