Impact of previous cesarean delivery on pregnancy and neonatal outcomes in subsequent in vitro fertilization/intracytoplasmic sperm injection and single frozen-thawed embryo transfer: a historical cohort study with a large sample size.

Purpose: This study aims to explore the impact of a woman's previous cesarean delivery (CD) on pregnancy and neonatal outcomes for subsequent in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) and single frozen-thawed embryo transfer (FET), compared with vaginal delivery (VD).

Methods: This was a retrospective cohort study that included a total of 5817 patients who desired to transfer a single vitrified-thawed blastocyst from the same oocyte retrieval cycle as their last live birth between January 2011 and January 2021 at a single reproductive medicine center. Patients with a single previous CD were classified in the CD group, while those with a single VD were assigned to the VD group. All patients underwent single blastocyst transfer. To minimize the effect of confounding factors, modified Poisson regression analyses with different adjustment models and propensity score matching (PSM) analyses were performed.

Results: Women with a previous CD had significantly lower rates of biochemical pregnancy, clinical pregnancy, and live births than those with a previous VD. Meanwhile, the CD rate was significantly higher in the CD group. There were no significant differences in the rates of multiple pregnancies, miscarriage, ectopic pregnancy, multiple live births, maternal complications, or preterm and neonatal outcomes.

Conclusions: A previous CD is associated with a significant reduction in the rates of biochemical pregnancy, clinical pregnancy, and live birth in patients undergoing subsequent single frozen-thawed blastocyst transfer. Additionally, it increases the rates of repeat CD.