Twin birth weight discordance: associated factors and outcome.

OBJECTIVE To determine the frequency of twin birth weight discordance and compare the maternal characteristics and neonatal outcome in discordant and concordant twin gestations. STUDY DESIGN Cross-sectional comparative study. PLACE AND DURATION OF STUDY MCH Centre, Unit-II, Pakistan Institute of Medical Sciences, Islamabad, from January 2005 to December 2007. METHODOLOGY All twin gestations delivered at > 28 weeks gestation were included. Birth weight discordance was defined as > 20% twin birth weight difference and two groups were developed accordingly. Prenatal complications, gestational age at delivery, mode of delivery and neonatal outcome were compared using chi-square and Fischer exact test with significance at p < 0.05. RESULTS Two hundred and fifty three pairs of twins were delivered during the three years. The frequency of birth weight discordance was 19% (48 verses 205 concordant twin pairs). Preterm delivery (68% vs. 25%), pre-labour rupture of membranes (33% vs. 9%) and pregnancy induced hypertension (22% vs. 12%) were significantly more frequent in birth weight discordant compared to concordant gestations. The cesarean section rate was 29% and 21% respectively. Twelve (12%) discordant and 29 (7%) concordant infants required NICU admission. There were 10 intrauterine deaths (10%) and one (1%) neonatal death among the discordant twins while 18 (4%) intrauterine deaths and 10 (2.4%) neonatal deaths occurred in concordant twins, resulting in uncorrected PNMR of 114.5 and 43.9 per 1000 births respectively. CONCLUSION Twin pregnancies with birth weight discordance are at higher risk of prenatal complications and have less favourable perinatal outcome. Their timely antenatal detection is, therefore, important for closer surveillance and timely delivery.