Impact of Caesarean section on pregnancy outcomes in ART after transfer of one or more frozen blastocysts.

INTRODUCTION:The prevalence of Caesarean delivery is rising steadily worldwide, and it is important to identify its future impact on fertility. A number of articles have been published on this subject, but the impact of Caesarean section on reproductive outcomes is still under debate, and none of these articles focus exclusively on frozen blastocysts. OBJECTIVE:The aim of this study was to evaluate the impact of a previous Caesarean delivery compared with a previous vaginal delivery on the chances of a live birth following the transfer of one or more frozen embryos at the blastocyst stage. METHODS:This was a retrospective, bicentric study at the University Hospitals of Nîmes and Montpellier, conducted between January 1st, 2016 and February 1st, 2021. Three hundred and ninety women with a history of childbirth and a transfer of one or more frozen embryos at blastocyst stage were included in the analysis. The primary outcome was the number of live births. Secondary outcomes were: the rate of positive HCG, miscarriage, ectopic pregnancy and clinical pregnancy, as well as the live birth rate according to the presence or absence of an isthmocele. RESULTS:Of the 390 patients included, 118 had a previous Caesarean delivery and 272 a vaginal delivery. No statistically significant differences were found for the primary (p = 0.9) or secondary outcomes. A trend towards lower live birth rates was observed in patients with isthmoceles, but this did not reach significance (p>0.9). On the other hand, transfers were more often described as difficult in the Caesarean delivery group (p = 0.011). CONCLUSION:Our study found no effect of previous Caesarean delivery on the chances of live birth after transferring one or more frozen blastocysts. However, further prospective studies are needed to confirm these results.