VARIATIONS IN COTININE LEVELS IN SMOKERS DURING AND AFTER PREGNANCY

OBJECTIVE: To compare the antenatal and postnatal cotinine levels in s moking women after controlling for the differences in smoking practice s. STUDY DESIGN: A paired comparison of two measurements of cotinine c oncentration was conducted in 40 smoking women voluntarily recruited i n a prenatal education program held in La Fe Hospital, Valencia, Spain , during 1990 and 1991. Cotinine concentration was assayed by gas chro matography in samples of saliva obtained during and after pregnancy. T he Wilcoxon matched-pairs test and multiple linear regression analysis were used. RESULTS: The cotinine per cigarette ratio during pregnancy (median 3.53 ng/ml per cigarette) was significantly lower than the ra tio in the postnatal testing (median 9.87 ng/ml per cigarette). This d ifference persisted after allowing for differences in reported cigaret te consumption, CONCLUSION: These findings suggest that the available equivalencies between cotinine level and nicotine intake obtained from adult nonpregnant populations cannot be directly applied during pregn ancy.