Our objective was to determine whether chorionicity affects umbilical cord blood acid-base parameters of the second twin. This was a retrospective cohort of twin pregnancies delivered at ≥23 weeks of gestation at a tertiary hospital from 2010 to 2016. Patients were included if arterial and venous umbilical cord gas results were available for both newborns and chorionicity was confirmed histologically. Exclusion criteria included intrauterine fetal demise of either twin prior to labor, major fetal anomalies, monoamnionicity, uncertain chronicity and twin-to-twin transfusion syndrome. The primary outcome evaluated was the umbilical artery (UA) pH of the second twin. A total of 593 dichorionic (DC) and 86 monochorionic (MC) twin pregnancies were included. No difference in UA pH was observed between MC and DC twins. Among vaginal deliveries (n = 97), the UA pH of the first twin was higher than the second twin (7.26 vs. 7.24; p = .01). Twin-to-twin delivery interval (TTDI) ≥20 min was associated with a higher UA pH in the first twin compared to the second twin (7.25 vs. 7.16, respectively; p = .006). Multivariable logistic regression was used to predict arterial pH < 7.20 for the second twin; the most predictive factors were arterial pH < 7.20 for the first twin, chronic hypertension and prolonged TTDI. Chorionicity was not associated with any acid-base parameter of umbilical cord blood in either the first or second twin. No differences in neonatal outcomes were observed based on chorionicity or birth order. Populations with a lower cesarean delivery rate may yield different findings.

中文翻译：

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绒毛膜性对二胎脐血酸碱分析的影响

我们的目标是确定绒毛膜性是否会影响第二对双胞胎的脐带血酸碱参数。这是 2010 年至 2016 年在一家三级医院在 ≥ 23 孕周分娩的双胎妊娠的回顾性队列。如果新生儿的动脉和静脉脐带气体结果均可用并且组织学证实绒毛膜性，则纳入患者。排除标准包括分娩前任一双胞胎的宫内胎儿死亡、主要胎儿异常、单羊膜、不确定的慢性和双胞胎输血综合征。评估的主要结果是第二对双胞胎的脐动脉 (UA) pH 值。共纳入 593 例双绒毛膜 (DC) 和 86 例单绒毛膜 (MC) 双胎妊娠。在 MC 和 DC 双胞胎之间没有观察到 UA pH 值的差异。在阴道分娩中（n= 97），第一个双胞胎的 UA pH 值高于第二个双胞胎（7.26 对 7.24；p= .01)。双胎分娩间隔 (TTDI) ≥20 分钟与第一个双胞胎相比第二个双胞胎的尿酸 pH 值更高（分别为 7.25 和 7.16；p= .006)。多变量逻辑回归用于预测第二对双胞胎的动脉 pH < 7.20；最具预测性的因素是第一对双胞胎的动脉 pH < 7.20、慢性高血压和 TTDI 延长。在第一对或第二对双胞胎中，绒毛膜性与脐带血的任何酸碱参数均无关。根据绒毛膜性或出生顺序，未观察到新生儿结局的差异。剖宫产率较低的人群可能会产生不同的结果。