title: Combined vaginal-cesarean delivery of twin pregnancies.
abstract: OBJECTIVE
  To estimate the incidence and factors associated with combined vaginal-cesarean delivery in twin pregnancies.
  
  
  METHODS
  We studied all twin births weighing 500 g or more during a 20-year period (1980-1999) at a tertiary care center. Major anomalies, monoamniotic and conjoined twins, and antepartum fetal deaths were excluded.
  
  
  RESULTS
  During this 20-year period, 105,987 women delivered, of whom 1565 (1.5%) had twins. Of these, 1151 twin sets fulfilled the study criteria. The mode of delivery was vaginal in 653 (56.8%), cesarean in 448 (38.9%), and vaginal-cesarean in 50 (4.3%). During the 20 years there was a statistically significant increase in combined vaginal-cesarean and elective cesarean deliveries, with a decrease in vaginal deliveries. Parity, gestational age, and birth weight discordance (>25%) were not associated with combined delivery. Compared with vaginal delivery, the nonvertex second twin was associated with a twofold higher risk of cesarean delivery (relative risk [RR] 2.3; 95% confidence interval [CI] 1.3, 3.8; P =.002); and an interdelivery interval of over 60 minutes with an eightfold higher risk (RR 8.2; CI 4.6,14.6; P <.001). Vaginal-cesarean delivery had a 22-fold higher use of general anesthesia compared with vaginal delivery (RR 21.8; CI 5.4, 88.5; P <.001).
  
  
  CONCLUSIONS
  There has been a significant increase in combined vaginal-cesarean and elective cesarean deliveries among twin gestations, with a decrease in vaginal births. Vaginal-cesarean delivery is associated with nonvertex second twin and a prolonged interdelivery interval.
authors.affiliation: Department of Obstetrics and Gynaecology, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: V L
authors.initials: VL
authors.lastname: Persad
authors.forename: T F
authors.initials: TF
authors.lastname: Baskett
authors.forename: C M
authors.initials: CM
authors.lastname: O'Connell
authors.forename: H M
authors.initials: HM
authors.lastname: Scott
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000401:mortality; D036861:Delivery, Obstetric / Q000401:mortality*; D005260:Female; D006801:Humans; D008499:Medical Records; D009674:Nova Scotia / Q000453:epidemiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D012189:Retrospective Studies; D014427:Twins