Does smoking influence serum alpha-fetoprotein levels in mid-trimester pregnancies?

The effect of cigarette smoking during pregnancy on serum alpha-fetoprotein (AFP) levels was studied in 1925 consecutive women at 16-18 weeks gestation who subsequently had liveborn singleton infants. Cotinine and AFP were measured in sera in all the women and answers to a smoking questionnaire were analysed in 894. Cotinine, a metabolic derivative of nicotine, serves as an objective measure of the average daily absorption of smoking products because of its relatively long half-life. Infants born to women who smoked were, on average, 198 g lighter than those born to non-smokers, even though maternal weights were comparable. Whether analysed by self-reporting or by serum cotinine, cigarette smoking had no measurable effect on serum AFP levels.