title: Congenital heart defects in a large, unselected cohort of monochorionic twins.
abstract: OBJECTIVE
  To determine the prevalence of congenital heart defects (CHDs) in a large, unselected cohort of monochorionic (MC) twins.
  
  
  METHODS
  We completed a chart review of all MC twin pregnancies in the Kaiser Permanente Northern California population from 1996 to 2003. CHDs were identified by diagnostic codes and confirmed by postnatal echocardiograms. Follow-up was obtained through one year of age.
  
  
  RESULTS
  A total of 926 liveborn MC twins met inclusion criteria. The prevalence of CHDs was 7.5%, 11.6 times the general population rate (CI 9.2 to 14.5). Septal defects were most common. 20% of infants with heart defects had twin-to-twin transfusion syndrome (TTTS) versus 8% of infants without defects (P<0.01); this association remained significant when controlling for potential confounders.
  
  
  CONCLUSIONS
  The prevalence of CHDs in this large cohort of MC twins was significantly higher than the general population rate, with TTTS an added risk factor.
authors.affiliation: Department of Reproductive Medicine, University of California, San Diego Health System, San Diego, CA 92103-8433, USA. kpettit@stanfordalumni.org
authors.forename: K E
authors.initials: KE
authors.lastname: Pettit
authors.forename: M
authors.initials: M
authors.lastname: Merchant
authors.forename: G A
authors.initials: GA
authors.lastname: Machin
authors.forename: T A
authors.initials: TA
authors.lastname: Tacy
authors.forename: M E
authors.initials: ME
authors.lastname: Norton
mesh_terms: D002140:California; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004200:Diseases in Twins / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics*; D004452:Echocardiography; D005260:Female; D005330:Fetofetal Transfusion / Q000453:epidemiology; D005500:Follow-Up Studies; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics*; D006343:Heart Septal Defects / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000235:genetics; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D012189:Retrospective Studies; D014430:Twins, Monozygotic