The association between prior cesarean delivery and subsequent in vitro fertilization outcomes in women undergoing autologous, frozen-thawed single euploid embryo transfer

Background The rates of cesarean deliveries continue to increase worldwide. Previous work suggests an association between a previous cesarean delivery and reduced fertility in natural conception and in vitro fertilization treatment cycles. To our knowledge, there is no published research that explored the relationship between a previous cesarean delivery and the clinical outcomes after in vitro fertilization and the subsequent transfer of a single frozen-thawed euploid embryo. Objective This study aimed to investigate the relationship between the previous mode of delivery and subsequent pregnancy outcomes in patients undergoing a single frozen-thawed euploid embryo transfer after in vitro fertilization. Study Design A retrospective cohort study was performed at a single academic fertility center from January 2012 to April 2020. All women with a history of a live birth undergoing autologous, frozen-thawed single euploid embryo transfers were identified. Cases included patients with a single previous cesarean delivery; controls included patients with a single previous vaginal delivery. Only the first embryo transfer cycle was included. The primary outcome was the implantation rate. Secondary outcomes included ongoing pregnancy and live birth rates, biochemical pregnancy rate, and clinical miscarriage rate. Results A total of 525 patients met the inclusion criteria and were included in the analysis. Patients with a previous cesarean delivery had a higher body mass index (24.5±4.5 vs 23.4±4.1; P=.004) than those in the vaginal delivery cohort; the rest of the demographic data were otherwise similar. In a univariate analysis, the implantation rate was significantly lower in patients with a previous cesarean delivery (111/200 [55.5%] vs 221/325 [68.0%]; P=.004). After adjusting for the relevant covariates, a previous cesarean delivery was associated with a 48% reduction in the odds of implantation (adjusted odds ratio, 0.52; 95% confidence interval, 0.34–0.78; P=.002). In addition, after adjusting for the same covariates, a previous cesarean delivery was significantly associated with a 39% reduction in the odds of an ongoing pregnancy and live birth (adjusted odds ratio, 0.61; 95% confidence interval, 0.41–0.90; P=.01). There were no differences in the biochemical pregnancy rates or clinical miscarriage rates. Conclusion This study demonstrated a marked reduction in implantation and ongoing pregnancy and live birth associated with a previous cesarean delivery in patients undergoing a single euploid embryo transfer. Our work stresses the importance of reducing the primary cesarean delivery rates at a national level and elucidating the mechanisms behind the substantially lower implantation rates after a cesarean delivery. The rates of cesarean deliveries continue to increase worldwide. Previous work suggests an association between a previous cesarean delivery and reduced fertility in natural conception and in vitro fertilization treatment cycles. To our knowledge, there is no published research that explored the relationship between a previous cesarean delivery and the clinical outcomes after in vitro fertilization and the subsequent transfer of a single frozen-thawed euploid embryo. This study aimed to investigate the relationship between the previous mode of delivery and subsequent pregnancy outcomes in patients undergoing a single frozen-thawed euploid embryo transfer after in vitro fertilization. A retrospective cohort study was performed at a single academic fertility center from January 2012 to April 2020. All women with a history of a live birth undergoing autologous, frozen-thawed single euploid embryo transfers were identified. Cases included patients with a single previous cesarean delivery; controls included patients with a single previous vaginal delivery. Only the first embryo transfer cycle was included. The primary outcome was the implantation rate. Secondary outcomes included ongoing pregnancy and live birth rates, biochemical pregnancy rate, and clinical miscarriage rate. A total of 525 patients met the inclusion criteria and were included in the analysis. Patients with a previous cesarean delivery had a higher body mass index (24.5±4.5 vs 23.4±4.1; P=.004) than those in the vaginal delivery cohort; the rest of the demographic data were otherwise similar. In a univariate analysis, the implantation rate was significantly lower in patients with a previous cesarean delivery (111/200 [55.5%] vs 221/325 [68.0%]; P=.004). After adjusting for the relevant covariates, a previous cesarean delivery was associated with a 48% reduction in the odds of implantation (adjusted odds ratio, 0.52; 95% confidence interval, 0.34–0.78; P=.002). In addition, after adjusting for the same covariates, a previous cesarean delivery was significantly associated with a 39% reduction in the odds of an ongoing pregnancy and live birth (adjusted odds ratio, 0.61; 95% confidence interval, 0.41–0.90; P=.01). There were no differences in the biochemical pregnancy rates or clinical miscarriage rates. This study demonstrated a marked reduction in implantation and ongoing pregnancy and live birth associated with a previous cesarean delivery in patients undergoing a single euploid embryo transfer. Our work stresses the importance of reducing the primary cesarean delivery rates at a national level and elucidating the mechanisms behind the substantially lower implantation rates after a cesarean delivery.