R. Lanni et al., BIRTH-WEIGHT DISCORDANCY IN TWINS - NEW DEFINITION AND STANDARD, European journal of obstetrics, gynecology, and reproductive biology, 76(1), 1998, pp. 37-40
Objective. The aim of this study was to improve the definition of birt
h weight discordancy based on its distribution in the population after
a correction in the unlike sex pairs. Study Design. The analysis was
conducted on 849 Italian twin pairs. Male's birth weight in the unlike
sex pairs was corrected by the physiological birth weight difference
estimated on 21.595 Italian twins data. Birth weight discordancy was c
omputed as a percentage of the larger twin's birth weight and it was c
ompared by sex pairs and by gestational ages (Kruskal-Wallis test). Ko
lmogorov-Smirnov test was used to fit a normal distribution to the squ
are-root transformed birth weight discordancy. Results. The estimated
physiological birth weight difference between males and females was 4.
39%, without any difference amen gestational ages. The 90th centile of
birth weight discordancy was 23.9% and the 95th centile was 29.2%. Co
nclusions. Ninetieth and 95th centiles of the fitted distribution are
proposed as cut-off values for the definition of mild and severe birth
weight discordancy. (C) 1998 Elsevier Science Ireland Ltd.