EFFECT OF MATERNAL SMOKING ON BIRTH-WEIGHT OF TWINS - A STUDY FROM THE DUTCH TWIN REGISTER

Since twins weigh about 20% less than singletons at birth, maternal sm oking may be a more severe risk for them than for singletons. Therefor e, the effect of maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a questionnaire filled out by the mother of the twins. Ge stational age explains more than 75% of the variance in birth weight. Other effects were tested with gestational age as a covariate. Apart f rom zygosity (DZ twins weigh more than MZ twins), birth order (first b orn twins weigh more than second born twins) and sex (boys weigh more than girls), there was a very significant birth weight reducing effect (more than 8%) maternal smoking as well as a significant influence of maternal age (young mothers give birth to smaller children). There we re no interactions with maternal smoking.