Does smoking influence serum α‐fetoprotein levels in mid‐trimester pregnancies?

Summary. The effect of cigarette smoking during pregnancy on serum α‐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.