Pregnancy and perinatal outcomes in pregnancies resulting from time interval between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer

Abstract

Background Adverse obstetric outcomes are correlated with altered circulating hormone levels at the time implantation by the trophectoderm. What’ more, embryo freezing process may also have adverse effect on perinatal outcomes. This study aims to evaluate whether increasing interval time between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer could have any effect on pregnancy and perinatal outcomes. Methods This was a retrospective cohort study included the first single blastocyst transfer in artificially cycles of all patients who underwent a freeze-all cycle between January 1st, 2016 and September 30th, 2018. All patients were divided into two groups according to the time interval between oocyte retrieval and the day of first frozen-thawed embryo transferred (FET): Group 1 (immediate FET cycles) and Group 2 (delayed FET cycles). Results No significant differences were reported between the two groups regarding the rates of clinical pregnancy, live birth, biochemical pregnancy and pregnancy loss even after adjusting for measured confounding. When accounting for perinatal outcomes, gestational age, birth weight, delivery mode, fetus gender, preterm birth, gestational hypertension, GDM, placenta previa, fetal malformation and low birthweight also did not vary significantly between the two groups. Only the incidence of macrosomia was more frequently in the Group 2 compared with the Group 1 (AOR 3.886, 95%CI 1.153–13.103, P = 0.029) after adjusting with a multiple logistic regression model. Conclusions We found delayed FET cycles for blastocyst transfer following freeze-all cycles may not improve the pregnancy outcomes. On the contrary, postponement of FET cycles may increase the risk of macrosomia. Therefore, FET cycles for blastocyst transfer should be done immediately to avoid adverse effects of delayed time on perinatal outcomes.

It is not worth postponing frozen embryo transfers after oocyte pickup: A retrospective cohort study based on propensity score matching

“…Does the length of interval between OPU and FET affects neonatal outcomes? Two recently published studies explored this issue but ended up with conflicting results ( 12 , 13 ). A study by Hu et al.…”

“…Does the length of interval between OPU and FET affects neonatal outcomes? Two recently published studies explored this issue but ended up with conflicting results (12,13). A study by Hu et al carried out single blastocyst transfers in patients and found that postponing FET was associated with an increased risk of macrosomia (13).…”

“…However, another study favored delaying FET ( 10 ). Recently, several investigations found that the interval between oocyte pickup (OPU) and FET did not affect LBR ( 11 – 13 ). These conflicting results may be attributed to different study designs, complex confounding factors such as controlled ovarian hyperstimulation (COH) protocols, endometrial preparation regimes, ovarian response, etc.…”

The Impact of Embryo Storage Time on Pregnancy and Perinatal Outcomes and the Time Limit of Vitrification: A Retrospective Cohort Study

“…However, he only focused on the patients aged 35-39 years when picking oocytes and blastocyst transfer cycles, which may cause selection bias. There were also several studies ( 14 , 25 , 26 ) comparing the reproductive outcomes between the immediate and delayed thawing cycles for vitrified embryos following a freeze-all strategy or a failed fresh embryo transfer. The pregnancy outcomes of the immediate cycles were comparable to the delayed cycles.…”

Effect of interval between oocyte retrieval and resuscitation embryo transfer on pregnancy outcomes

“…Previous metaanalyses have not come to a de nitive conclusion on how immediate or delayed resuscitation bene t pregnancy rates [7,8]. Additionally, many of the retrospective studies [9][10][11] in the literature were conducted years ago, and the results of these studies may be biased against changes in the existing COH protocols.…”