Alpha-fetoprotein (AFP) quantitation in maternal blood has been used for prenatal diagnosis of
anencephaly, spina bifida and some other
congenital abnormalities. The levels of AFP in pregnancy serum are greatly dispersed within each gestational period, what makes the test of difficult interpretation mainly in border line cases. The factors which contribute to this variability are still poorly understood. They must act either on the synthesis or catabolism of the
protein, or on the permeability of the fetal-maternal barrier. In an attempt to elucidate some of these factors, the levels of AFP in serum of 89 women at 32 to 34 weeks gestation and of 115 women at term were measured by radioimmunoassay and related to several obstetric variables such as parity, pregnancy number, 1 - minute Apgar score, smoking habit and sex of newborn. It was seen that parity and pregnancy number do not correlate with the levels of AFP in pregnancy serum. Smokers, particularly those who
smoke more than a pack per day, however, had higher levels of the
protein in their blood. The interpretation of these data should take into consideration the fact that smoking causes vasoconstriction and important vascular alterations similar to the ones encountered in
diabetic angiopathy. It is possible that an increased microvascular permeability of placenta and/or membranes to
proteins of the size of AFP from the fetus to maternal circulation may explain the greater levels of the
protein in serum of smokers.(ABSTRACT TRUNCATED AT 250 WORDS)