The source of error in the estimation of intertwin birth weight discordance.
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.
Reberdao
Maria Augusta
MA
Prenatal Diagnosis Center, Hospital Garcia de Orta, Almada, Portugal.
Martins
Luisa
L
Torgal
Mariana
M
Viana
Rui
R
Seminova
Tatiana
T
Casal
Ester
E
Hermida
Manuel
M
Blickstein
Isaac
I
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*