Fertility and pregnancy outcomes after a uterine niche resection in women with and without infertility: a systematic review and meta-analysis

Objective: To assess the effect of a uterine niche resection on fertility and pregnancy outcomes. We compared these outcomes in women with and without infertility, as we hypothesized that in the group with infertility, the presence of the niche may contribute to the failure to conceive. The focus on reproductive and pregnancy outcomes as well as the differentiation in study populations is novel and has not been a topic of research up until now. Evidence Review: The databases PubMed, Embase, and Web of Science were systematically searched in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines from inception until July 19, 2021. Randomized controlled trials (RCTs), cohort studies, case-control studies, and case series with at least 10 women were included if they reported fertility and/or pregnancy outcomes after any type of niche surgery among women with infertility or without the diagnosis of infertility. The risk of bias and quality of the included studies were assessed using the Cochrane risk-of-bias tool, the Newcastle-Ottawa Scale, and a set of niche-specific criteria. The primary outcome was live birth rate. The secondary outcomes included pregnancy and miscarriage rates, occurrence of an ectopic pregnancy, uterine dehiscence, and other obstetric complications. A meta-analysis was performed for the outcomes live birth, pregnancy, and miscarriage rates. The proportion with corresponding 95% confidence interval (CI) was calculated for each individual study, stratified for type of surgery and fertility status. Results: A total of 3,825 records were identified, of which 21 articles were included (1 RCT, 1 case series, and 5 prospective and 14 retrospective cohort studies). The RCT compared a surgical intervention with expectant management, whereas the other studies had an observational design. Sixteen studies reported on fertility outcomes in women with infertility (n = 648), and 5 studies reported on fertility outcomes in women without a diagnosis of infertility (n = 237). The reported surgical procedures were hysteroscopic niche resection (HNR) (n = 14), vaginal niche resection (n = 7), laparoscopic niche resection (n = 7), and laparotomic niche resection (n = 2). The overall methodological quality of included studies was moderate to poor with a high risk of bias. The statistical heterogeneity among the included studies ranged between 0 and 88%. Overall, the effect of a niche resection on the live birth rate was lower in women without infertility than in women with infertility: 36% (95% CI, 26 %–46%) vs. 54% (95% CI, 44%–64%).The live birth rates per different operative technique showed similar trends: HNR, 52% (95% CI, 40%–64%) vs. 55% (95% CI, 38%–71%); laparoscopic niche resection, 36% (95% CI, 25%–48%) vs. 42% (95% CI, 30%–55%); and vaginal niche resection, 25% (95% CI, 9%–46%) vs. 60% (95% CI, 52%–67%). The only RCT performed showed a significantly higher pregnancy rate after HNR than that after expectant management (N = 61 women; relative risk, 2.41; 95% CI, 1.32–4.39) in women diagnosed with infertility. There were no significant differences in the pregnancy and miscarriage rates between the different populations. A cesarean scar pregnancy was reported in 0.97% of pregnancies. After a hysteroscopic approach, in 4 (2.8%) of 145 deliveries, a uterine dehiscence or rupture was reported. There was no uterine dehiscence described after the other niche interventions. Conclusion: On the basis of the current available data, it is not advised to perform a niche resection to improve fertility outcomes. Well-designed comparative studies are necessary to investigate whether there is a role for niche surgery in patients with regard to fertility outcomes.