Fetal and neonatal mortality among twin gestations in a Canadian population: the effect of intrapair birthweight discordance.
The purpose of this study was to examine the association between intrapair birthweight discordance and fetal and neonatal mortality. This was a historical cohort study, using the Statistics Canada linked birth-infant death file. Twin births in Canada (excluding Ontario) for the period 1986-1997 were studied. Outcome measures were fetal and neonatal mortality. Among 59,034 twin births, 53% had 0 to 9% birthweight difference; 30% had 10 to 19% discordance; 11% had 20 to 29% discordance; and 6% had > or = 30% discordance. Maternal age, parity, sex discordance, and gestational age were important factors affecting birth weight discordance. Fetal death rates were 0.95, 1.26, 3.14, and 11.10%, respectively, in infants with a birthweight discordance of 0 to 9, 10 to 19, 20 to 29, and > or = 30%. Corresponding figures for neonatal death rates were 1.90, 2.32, 3.05, and 8.86%, respectively. Adjustment for important confounding variables including the actual birthweight and gestational age substantially reduced the birthweight discordance-related risk of fetal and neonatal mortality, but the results remained statistically significant and clinically important. The birthweight discordance-related risk of fetal and neonatal mortality was higher in smaller twins than in larger twins and higher in infants with gestational age > or = 37 weeks than those < 37 weeks. Birthweight discordance is an important risk factor for fetal and neonatal mortality, and the birthweight discordance-related risk of fetal and neonatal mortality is higher in smaller twins than in larger twins and higher in term twins than in preterm twins.
Wen
Shi Wu
SW
Health Surveillance and Epidemiology Division, Centre for Healthy Human Development, Health Canada, Ottawa, Ontario, Canada.
Fung
Karen Fung Kee
KF
Huang
Ling
L
Demissie
Kitaw
K
Joseph
K S
KS
Allen
Alexander C
AC
Kramer
Michael S
MS
D000328:Adult; D001724:Birth Weight; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000401:mortality*; D006801:Humans; D007226:Infant Mortality / Q000639:trends*; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D012307:Risk Factors; D014427:Twins