Maternal tobacco exposure and cotinine levels in fetal fluids in the first half of pregnancy.

OBJECTIVE: To evaluate the distribution of cotinine in fetal fluids and serum during the first half of pregnancy, and compare the fetal and maternal cotinine levels in passive and active smokers.
METHODS: Maternal smoking status was determined by questionnaire in 85 pregnant women requesting abortion for psychosocial reasons between 7 and 17 weeks' gestation. Coelomic and amniotic fluid samples were collected between 7 and 11 weeks and fetal blood and amniotic fluid between 11 and 17 weeks. Cotinine levels were measured by radioimmunoassay.
RESULTS: Women classified themselves as nonsmokers in 40 cases, passive smokers in 19 cases, and voluntary smokers in 26 cases. Five nonsmokers, 16 passive smokers, and all smokers had cotinine levels above the detection limit of the assay. Cotinine was invariably found in coelomic, amniotic, and fetal serum when maternal serum and urine cotinine levels exceeded 25 and 250 ng/mL, respectively. Higher cotinine levels were found in fetal fluids and serum than in maternal serum. Positive linear correlations were found between maternal urine and amniotic fluid cotinine concentrations (r = .75), between maternal urine cotinine concentration and number of cigarettes smoked per day (r = .66), and between maternal and fetal serum cotinine concentrations (r = .97).
CONCLUSION: Cotinine accumulates in the fetal compartments as early as 7 weeks' gestation in both active and passive smokers. Women should be advised to give up smoking from conception and avoid environmental tobacco smoke exposure.