title: The source of error in the estimation of intertwin birth weight discordance.
abstract: to assess the accuracy of paired estimated fetal weights (EFWs) to predict three levels of twin birth weight discordance (>15%, >20% and >25%).
  
  
  
  a cohort of twin pairs underwent ultrasound examinations within 2 weeks from birth. We calculated the frequency of under- and overestimation of the actual birth weight (< or >10%, respectively) in the entire cohort as well in the subset of mono- and dichorionic pairs.
  
  
  
  discordance was largely underestimated (observed 10.4 ± 0.8% compared to actual 19.2 ± 1.1%, P=0.001) because the larger twin was more frequently underestimated [30.6 vs. 17.7%, odds ratio (OR) 2.0, 95% confidence interval (CI) 1.1, 3.9 in the entire cohort, and 34.2 vs. 13.1%, OR 3.4, 95% CI 1.4, 8.4 in the dichorionic pairs]. Overall, the specificity for detecting the three levels of discordance was adequate (91.5-94.2%) but the sensitivity was poor (11.1-17.8%) and tended to decrease with increasing discordance level.
  
  
  
  the poor ability of paired EFWs to diagnose birth weight discordance results from underestimation of the larger twin.
authors: Prenatal Diagnosis Center, Hospital Garcia de Orta, Almada, Portugal.
authors: Maria Augusta
authors: MA
authors: Reberdao
authors: Luisa
authors: L
authors: Martins
authors: Mariana
authors: M
authors: Torgal
authors: Rui
authors: R
authors: Viana
authors: Tatiana
authors: T
authors: Seminova
authors: Ester
authors: E
authors: Casal
authors: Manuel
authors: M
authors: Hermida
authors: Isaac
authors: I
authors: Blickstein
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000502:physiology*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014427:Twins / Q000502:physiology*; D016216:Ultrasonography, Prenatal / Q000379:methods*