Determinants of birthweight of twins

Abstract

The low birthweight of twins compared with singletons is only slightly influenced by the higher congenital abnormality rate in twins, or the increased incidence of proteinuric pre-eclampsia in the mothers. Reduced intakes of energy food or of zinc, copper, and iron do not account for the lower birthweight. The main cause of low birthweight is preterm delivery, and this is more common in monozygotic than dizygotic twin pregnancies, due particularly to premature rupture of the membranes. The type of placentation did not influence the preterm onset of labor. Preterm labor in monozygotic twin pregnancies is associated with a very high boy:girl ratio, but this did not apply in dizygotic twin pregnancies.