title: Is Cesarean Delivery Preferable in Twin Pregnancies at >=36 Weeks Gestation?
abstract: The optimal mode of delivery in twin pregnancies remains controversial. A recent randomized trial did not find any benefit of planned cesarean vs. vaginal delivery at 32-38 weeks gestation, but the trial was not powered to detect a moderate effect. We aimed to evaluate the impact of cesarean delivery on perinatal mortality and severe neonatal morbidity in twin pregnancies at ≥32 weeks through a large database exploration approach with the power to detect moderate risk differences.
  
  
  
  In a retrospective birth cohort study using the U.S. matched multiple births, 1995-2000 (the available largest multiple birth dataset), we compared perinatal outcomes in twins (n = 181,810 pregnancies) delivered at 32-41 weeks gestation without congenital anomalies. The primary outcome was a composite of perinatal death and severe neonatal morbidity. Cox regression was used to estimate the adjusted hazard ratio (aHR) controlling for the propensity to cesarean delivery, fetal characteristics (sex, birth weight, birth weight discordance, same-sex twin or not) and twin-cluster level dependence. Prospective risks were calculated using the fetuses-at-risk denominators.
  
  
  
  The overall rates of the primary outcome were slightly lower in intended cesarean (6.20%) vs. vaginal (6.45%) deliveries. The aHRs of the primary outcome were in favor of vaginal delivery at 32 (aHR = 1.06, p = 0.03) or 33 (aHR = 1.22, p<0.001) weeks, neutral at 34-35 weeks, but in favor of cesarean delivery at 36 (aHR = 0.94, p = 0.004), 37, 38 and 39+ weeks (aHR: 0.72 to 0.78, all p<0.001). The lower risk of the primary outcome for cesarean vs. vaginal deliveries at 36+ weeks of gestation remained when the analyses were restricted to different-sex (dichorionic) twins (aHR = 0.84, 95% CI 0.80-0.88).
  
  
  
  Cesarean delivery may be beneficial for perinatal outcomes overall in twin pregnancies at ≥36 weeks gestation.
authors.affiliation: Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.
authors.forename: Yu
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.|Department of Obstetrics and Gynecology, Sainte-Justine Hospital, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Zhong-Cheng
authors.initials: ZC
authors.lastname: Luo
authors.affiliation: Department of Obstetrics and Gynecology, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.
authors.forename: Zu-Jing
authors.initials: ZJ
authors.lastname: Yang
authors.affiliation: Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200030.
authors.forename: Yu-Na
authors.initials: YN
authors.lastname: Guo
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah and Intermountain Health Care, Utah, United States of America.
authors.forename: Ware
authors.initials: W
authors.lastname: Branch
authors.affiliation: Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China 200092.
authors.forename: Hong
authors.initials: H
authors.lastname: Huang
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000401:mortality*; D036861:Delivery, Obstetric / Q000379:methods / Q000401:mortality*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D015931:Intensive Care, Neonatal; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D015996:Survival Rate; D055815:Young Adult