[Growth discordance in dichorionic twin pregnancies: risk factors, diagnosis and management].

Objective: To analyse the risk factors and perinatal consequences of growth discordance among dichorionic twin pregnancies. Subjects and methods. A cohort of 346 dichorionic twin pregnancies delivered at one institution between January 1996 and December 1999 was analyzed. Two groups were compared, according to the presence or absence of growth discordance (n=72 and 274, respectively). Birth weight discordance was defined as a difference of 20% or more of the weight of the heavier twin, associated with an intra-uterine growth restriction (10(th) percentile) of at least one twin. Ultrasound discordance was defined as a difference of estimated fetal weight>20%. The two groups were compared by univariate and multivariate analysis.

Results: The main risk factors for birth weight discordance in multivariate analysis were ovulation induction (OR=1.6 [1.0-2.4]), multifetal pregnancy reduction (OR=2.3 [1.3-4.2]), and fetal malformations (OR=2.4 [1.0-5.4]). Ultrasound shows a poor performance in predicting discordance with a sensitivity of 55.6%, a specificity of 94.2%, a positive predictive value of 71.4% and a negative predictive value of 89.0%. Birth weight discordance was associated with a poor fetal and neonatal outcome: gestational age at delivery was 34.4 weeks versus 35.4 weeks, there were more caesarean deliveries (OR=1.9 [1.3-2.8]), a higher perinatal mortality (OR=3.7 [1.6-8.5]), and more neonatal intensive care unit admissions (OR=1.8 [1.2-2.7]). Multivariate analysis shows that growth discordance is an independent risk factor for mortality but not for cerebral adverse outcome or respiratory distress syndrome.

Conclusion: Ovulation induction and multifetal pregnancy reduction are independent risk factors for twin birth weight discordance, which carries a poor perinatal prognosis.