Smoking in pregnancy: relation of birth weight to maternal plasma carotene and cholesterol levels.

Not all mothers who smoke during pregnancy deliver small infants. Nutritional supplementation during pregnancy apparently protects the fetuses of some mothers. Our previous studies showed that plasma levels of carotene and cholesterol were correlated with birth weight. The present study examined the association between mid-pregnancy plasma levels of carotene and cholesterol and subsequent birth weight. In a prospective study of 388 women (47.8% smokers), levels of plasma nutrients and demographic and anthropometric measurements were obtained at 19 and 36 weeks' gestation and related to indices of infant size at birth. In non-smokers, the level of plasma cholesterol at mid-pregnancy correlated positively with birth weight. In contrast, in mothers who smoked more than ten cigarettes daily, the relationship of cholesterol to birth weight was dependent on the simultaneously observed level of plasma carotene. When plasma cholesterol and carotene concentrations were both low at mid-pregnancy, birth weight was low. On the other hand, when the carotene level was high and the cholesterol level low, birth weight was at least equivalent to that of non-smokers. The interactive effect of smoking, cholesterol, and carotene on birth weight was significant (P = .017) after adjusting for gestational age, sex, prenatal care, race, previous low birth weight infants, parity, weight at mid-pregnancy, and total weight gain during pregnancy. Among smokers, the smallest infants were born to mothers having the greatest decrease in plasma carotene between 19-36 weeks' gestation. Smokers whose plasma carotene remained constant or increased had larger infants; a similar association was not observed for cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)