Department of Obstetrics and Gynecology, Stavanger University Hospital, Stavanger, Norway.
Department of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway.
Acta Obstet Gynecol Scand. 2024 Sep;103(9):1888-1897. doi: 10.1111/aogs.14929. Epub 2024 Jul 24.
In clinical experience, occiput posterior (OP) position is associated with longer labor duration than occiput anterior (OA) position, but few studies have investigated the association between labor duration and fetal position. We aimed to compare duration of the active phase of labor in OP deliveries with OA deliveries in a contemporary population using survival methods. Secondary aims were to compare the frequencies of operative interventions, obstetric anal sphincter injuries (OASIS), postpartum hemorrhage, and newborn outcomes in OP with OA deliveries.
We did a historical cohort study in three university hospitals in Norway from 2012 to 2022. Women with a single fetus in cephalic presentation, no previous cesarean section and gestational age ≥37 weeks were eligible and stratified into the first four groups of the Robson ten-group classification system (TGCS). We estimated the mean duration and calculated the hazard ratio (HR) for delivery using survival analyses. Cesarean sections and instrumental vaginal deliveries were censored.
The study population comprised 112 019 women, 105 571 (94.2%) were delivered in OA and 6448 (5.8%) in OP position. The estimated mean duration of the active phase of labor was longer in women with the fetus in OP position in all four TGCS groups. The estimated duration was longer in the OP groups in analyses stratified with respect to epidural analgesia and oxytocin augmentation. The graphical abstract illustrates the probability of delivery in OP compared with OA position in merged TGCS groups 1 and 2a, as a function of time. The unadjusted HR was 0.33 (95% CI 0.31-0.36) for fetuses delivered in OP position compared with OA position in TGCS group 1, 0.25 (95% CI 0.21-0.27) in group 2a, 0.70 (95% CI 0.67-0.73) in group 3, and 0.61 (95% CI 0.55-0.67) in group 4a, respectively. Neither maternal age, gestational age, BMI nor birthweight had confounding effect. Operative delivery rates and OASIS rates were higher in OP position in all four groups.
We found longer duration of the active phase of labor in women with the fetus delivered in OP position in all four TGCS groups.
在临床经验中，枕后位（OP）的分娩持续时间长于枕前位（OA），但很少有研究调查分娩持续时间与胎儿位置之间的关系。我们旨在使用生存方法比较现代人群中 OP 分娩与 OA 分娩活跃期的持续时间。次要目的是比较 OP 与 OA 分娩的手术干预、产科肛门括约肌损伤（OASIS）、产后出血和新生儿结局的发生率。
我们在挪威的三所大学医院进行了一项历史队列研究，时间为 2012 年至 2022 年。符合条件的孕妇为单胎头位，无既往剖宫产且孕周≥37 周，并分为 Robson 十组分类系统（TGCS）的前四组。我们使用生存分析估计平均持续时间并计算分娩的风险比（HR）。剖宫产和器械性阴道分娩被截尾。
研究人群包括 112019 名女性，105571 名（94.2%）为 OA 分娩，6448 名（5.8%）为 OP 分娩。在所有四组 TGCS 中，胎儿处于 OP 位置的女性活跃期的估计平均持续时间较长。在分层分析中，接受硬膜外镇痛和催产素强化的 OP 组的估计持续时间较长。图形摘要说明了在合并的 TGCS 组 1 和 2a 中，OP 与 OA 位置相比，分娩的概率作为时间的函数。在 TGCS 组 1 中，OP 分娩的未调整 HR 为 0.33（95%CI 0.31-0.36），组 2a 为 0.25（95%CI 0.21-0.27），组 3 为 0.70（95%CI 0.67-0.73），组 4a 为 0.61（95%CI 0.55-0.67）。母亲年龄、胎龄、BMI 或出生体重均无混杂作用。在所有四组中，OP 位置的剖宫产率和 OASIS 率均较高。
我们发现，在所有四组 TGCS 中，胎儿处于 OP 位置的女性活跃期的持续时间较长。
