Cigarette consumption and serum cotinine in relation to birthweight

Abstract

The concentration of serum cotinine (the major metabolite of nicotine) was measured in sera from 4211 women at between 15 and 21 weeks gestation to determine whether a serum cotinine level was a better predictor of low birthweight than the self‐reported number of cigarettes smoked per day. Both cotinine levels and smoking history were significantly associated with reduced birthweight, but cotinine correlated significantly better. Smokers of ≤25 cigarettes per day, representing the 2·7% of women with the greatest cigarette consumption, had infants 289 g lighter than the 68% of women who were non‐smokers. Women with serum cotinine levels in the top 2·7% (≤284 ng/ml) had infants 441 g lighter than the 68% of women with the lowest cotinine levels (≤24 ng/ml). Our results strengthen the evidence linking smoking with low birthweight and also demonstrate that cotinine can be satisfactorily used to assess and monitor cigarette smoking in pregnancy.