Department of Obstetrics and Gynecology, Faculty of Health Sciences, McMaster University (Drs Muraca, Kirubarajan, and Rottenstreich), Hamilton, Canada; Department of Health Research Methods, Evidence and Impact, Faculty of Health Sciences, McMaster University (Dr Muraca), Hamilton, Canada; Clinical Epidemiology Unit, Department of Medicine, Solna, Karolinska Institutet (Dr Muraca), Stockholm, Sweden.
Department of Obstetrics and Gynecology, Shaare Zedek Medical Center, Hebrew University School of Medicine (Drs Peled, Weiss, Sela, Grisaru-Granovsky, and Rottenstreich), Jerusalem, Israel.
Am J Obstet Gynecol MFM. 2024 Apr;6(4):101326. doi: 10.1016/j.ajogmf.2024.101326. Epub 2024 Mar 5.
An increased risk for preterm birth has been observed among individuals with a previous second stage cesarean delivery when compared with those with a previous vaginal delivery. One mechanism that may contribute to the increased risk for preterm birth following a second stage cesarean delivery is the increased risk for cervical injury because of extension of the uterine incision (hysterotomy) into the cervix. The contribution of hysterotomy extension to the rate of preterm birth in a subsequent pregnancy has not been investigated and may shed light on the mechanism underlying the observed relationship between the mode of delivery and subsequent preterm birth.
We aimed to quantify the association between unintended hysterotomy extension and preterm birth in a subsequent delivery.
We performed a retrospective cohort study using electronic perinatal data collected from 2 university-affiliated obstetrical centers. The study included patients with a primary cesarean delivery of a term, singleton live birth and a subsequent singleton birth in the same catchment (2005-2021). The primary outcome was subsequent preterm birth <37 weeks' gestation; secondary outcomes included subsequent preterm birth at <34, <32, and <28 weeks' gestation. We assessed crude and adjusted associations between unintended hysterotomy extensions and subsequent preterm birth with log binomial regression models using rate ratios and 95% confidence intervals. Adjusted models included several characteristics of the primary cesarean delivery such as maternal age, length of active labor, indication for cesarean delivery, chorioamnionitis, and maternal comorbidity.
A total 4797 patients met the study inclusion criteria. The overall rate of unintended hysterotomy extension in the primary cesarean delivery was 6.0% and the total rate of preterm birth in the subsequent pregnancy was 4.8%. Patients with an unintended hysterotomy extension were more likely to have a longer duration of active labor, chorioamnionitis, failed vacuum delivery attempt, second stage cesarean delivery, and persistent occiput posterior position of the fetal head in the primary cesarean delivery and higher rates of smoking in the subsequent pregnancy. Multivariable analyses that controlled for several confounders showed that a history of hysterotomy extension was not associated with a higher risk for preterm birth <37 weeks' gestation (adjusted rate ratio, 1.55; 95% confidence interval, 0.98-2.47), but it was associated with preterm birth <34 weeks' gestation (adjusted rate ratio, 2.49; 95% confidence interval, 1.06-5.42).
Patients with a uterine incision extension have a 2.5 times higher rate of preterm birth <34 weeks' gestation when compared with patients who did not have this injury. This association was not observed for preterm birth <37 weeks' gestation. Future research should aim to replicate our analyses with incorporation of additional data to minimize the potential for residual confounding.
与阴道分娩相比，先前行第二产程剖宫产的患者早产风险增加。第二产程剖宫产导致子宫切口（剖宫产术）延伸至宫颈，从而增加宫颈损伤风险，这可能是导致随后早产风险增加的机制之一。子宫切口延伸对随后妊娠早产率的影响尚未得到研究，这可能有助于阐明分娩方式与随后早产之间观察到的关系的潜在机制。
我们旨在量化后续分娩中意外子宫切口延伸与早产之间的关联。
我们使用从 2 家大学附属产科中心收集的电子围产期数据进行了回顾性队列研究。该研究纳入了行初次足月、单胎活产并在同一区域再次分娩的患者（2005-2021 年）。主要结局为后续早产<37 周；次要结局包括<34 周、<32 周和<28 周的早产。我们使用对数二项式回归模型评估了未计划的子宫切口延伸与随后早产之间的粗关联和调整关联，使用率比和 95%置信区间。调整模型包括初次剖宫产的几个特征，如产妇年龄、活跃分娩时长、剖宫产指征、绒毛膜羊膜炎和产妇合并症。
共有 4797 名患者符合研究纳入标准。初次剖宫产中意外子宫切口延伸的总体发生率为 6.0%，随后妊娠的早产总发生率为 4.8%。有意外子宫切口延伸的患者活跃分娩时间更长、绒毛膜羊膜炎、真空辅助分娩失败、第二产程剖宫产和胎儿头枕后位持续的可能性更高，且随后妊娠的吸烟率更高。控制了几个混杂因素的多变量分析表明，子宫切口延伸史与早产<37 周的风险增加无关（调整后率比，1.55；95%置信区间，0.98-2.47），但与早产<34 周有关（调整后率比，2.49；95%置信区间，1.06-5.42）。
与未发生这种损伤的患者相比，子宫切口延伸的患者早产<34 周的风险增加 2.5 倍。这种关联在早产<37 周时未观察到。未来的研究应旨在通过纳入额外数据来重复我们的分析，以最大程度地减少潜在的残余混杂。
