Placental transfer of cotinine at 12–17 weeks of gestation and at term in heavy smokers

The objective of this study was to compare the placental transfer of cotinine from maternal to fetal circulation in heavy chronic smokers during the second trimester of pregnancy and at term. Maternal and fetal cotinine concentrations were evaluated in 26 women requesting surgical termination for psychosocial reasons at 12–17 weeks gestation and 26 women with uncomplicated pregnancies at 37–40 weeks gestation, and delivered vaginally. Cotinine concentrations were measured by radioimmunoassay. At 12–17 weeks, the median cotinine concentration was significantly (P = 0.009) lower in fetal than in maternal serum. At term fetal and maternal cotinine concentrations were similar. The feto–maternal ratio was significantly (P < 0.001) lower in second trimester pregnancies than in term pregnancies. In both groups, positive linear correlations were found between maternal and fetal serum cotinine concentration and between maternal serum cotinine concentration and the number of cigarettes smoked per day. These data indicate that placental cotinine transfer increases with advancing gestation. This may be secondary to increased placental permeability in the third trimester, which could be linked to progressive placental damage in heavy chronic smokers.SCOPUS: ar.j