title: Impact of anomalous triplets on morbidity outcomes of normal in utero siblings.
abstract: OBJECTIVE
  To evaluate the impact of number of anomalous fetuses on the prevalence of very preterm births (< 32 weeks), very low birth weight (< 1,500 g), and small for gestational age (SGA) infants among their normal cotriplets.
  
  
  METHODS
  Cross-sectional study of United States triplet births from 1995 to 2000 using Matched Multiple Birth Files, comparing outcomes for triplet sets with no anomalous, 1 anomalous, and 2 anomalous fetuses. Chi-square test for trend and multiple logistic regression analyses, applying generalized estimating equations to account for correlation among cotriplets, were implemented.
  
  
  RESULTS
  Of 34,881 matched triplets, 34,104 (97.8%) were nonanomalous (2.2% prevalence of fetal anomaly). Prevalence of very preterm birth (P < .001) and very low birth weight (P < .001), but not SGA (P = .52), among nonanomalous births increased significantly with number of anomalous cotriplets. The prevalence of very preterm birth was 44.1%, 54.8%, and 68.8%, respectively, as number of anomalous triplets per set increased from none to two. The prevalence of very low birth weight was 32.3%, 39.6%, and 62.0%, respectively. These trends remained unchanged after adjustment for correlation and potential confounding.
  
  
  CONCLUSIONS
  Prevalence of triplet births with gestation less than 32 weeks and birth weight less than 1,500 g, but not SGA, among nonanomalous triplets increase linearly with number of anomalous members within triplet sets.
  
  
  METHODS
  III.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Center for Research in Women's Health, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA. alan.tita@obgyn.uab.edu
authors.forename: Alan T N
authors.initials: AT
authors.lastname: Tita
authors.forename: Hamisu M
authors.initials: HM
authors.lastname: Salihu
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Ramsey
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D000013:Congenital Abnormalities / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D011247:Pregnancy; D011256:Pregnancy Outcome; D015995:Prevalence; D014310:Triplets