The distribution of intra-twin birth weight discordance and its association with total twin birth weight, gestational age, and neonatal mortality.
OBJECTIVE
To determine an appropriate cutoff value to differentiate physiologic and pathologic birth weight discordance, to determine the prevalence of birth weight discordance > or =25% among twin pregnancies in different sub-populations, and to examine its clinical significance.


METHODS
Historical cohort study of 147,262 twin sets registered in the United States between 1995 and 1997.


RESULTS
The prevalence of birth weight discordance > or =25% among twin pregnancies was 8.6%. The prevalence of birth weight discordance > or =25% was significantly decreased with increasing total twin birth weight deciles, was more frequently found in twins with discordant gender (9.1%) than in those twins with concordant gender (8.3%) and in mothers whose age was 30 years or older (9.1%) than those of younger mothers (8.1%). Birth weight discordance > or =25% was associated with earlier gestational age at delivery (35.0 weeks versus 36.0 weeks) and higher neonatal mortality (5.4% versus 2.3%) as compared to twins with lower birth weight discordance.


CONCLUSIONS
The prevalence of birth weight discordance > or =25% among twin pregnancies was 8.6%, which is associated with lower gestational age at delivery and higher neonatal mortality rates, and may represent a pathologic process.
Tan
Hongzhuan
H
OMNI Research Group, Department of Obstetrics & Gynecology, Faculty of Medicine, University of Ottawa, Ont., Canada.
Wen
Shi Wu
SW
Fung Kee Fung
Karen
K
Walker
Mark
M
Demissie
Kitaw
K
D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D008423:Maternal Age; D016017:Odds Ratio; D011247:Pregnancy; D011272:Pregnancy, Multiple; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D014427:Twins