title: Twin chorionicity and pre-eclampsia.
abstract: OBJECTIVE
  To determine whether the incidence of pre-eclampsia is different in dichorionic compared to monochorionic twin pregnancies.
  
  
  METHODS
  The study involved 666 twin pregnancies resulting in two live births after 24 weeks of gestation. Ultrasound examination at 10-14 weeks of gestation demonstrated that 171 (25.7%) were monochorionic and 495 (74.3%) were dichorionic twins. Pregnancy outcome information regarding the development of pre-eclampsia was obtained from the maternity units. The incidence of pre-eclampsia in the dichorionic and monochorionic twin pregnancies was compared.
  
  
  RESULTS
  The incidence of pre-eclampsia in monochorionic twin pregnancies (9.4%) was not significantly different from that in dichorionic pregnancies (7.3%) ( P = 0.48). Multiple logistic regression revealed that chorionicity has no effect on the development of pre-eclampsia after adjusting for maternal age, ethnic group, maternal smoking, parity and gestational age at delivery ( P = 0.6; odds ratio for monochorionic compared with dichorionic twin pregnancies, 1.19; 95% confidence interval, 0.61-2.3).
  
  
  CONCLUSIONS
  In twin pregnancies chorionicity does not affect the incidence of pre-eclampsia.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: M D
authors.initials: MD
authors.lastname: Savvidou
authors.forename: E
authors.initials: E
authors.lastname: Karanastasi
authors.forename: C
authors.initials: C
authors.lastname: Skentou
authors.forename: L
authors.initials: L
authors.lastname: Geerts
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000328:Adult; D002823:Chorion / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D016017:Odds Ratio; D011225:Pre-Eclampsia / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000209:etiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011272:Pregnancy, Multiple; D012307:Risk Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal