Smoking during pregnancy: comparison of self-reports and cotinine levels in 496 women.

Objective: To validate self-reported smoking habits in smoking pregnant women and estimate the prevalence of substantial exposure to passive smoking in non-smoking pregnant women.

Design: Retrospective, quantitative study, consecutively collected samples.

Setting: One antenatal clinic in Blekinge County, Sweden.

Subjects: 509 pregnant women.

Method: Information about smoking habits were taken from the antenatal records of 496 women (97%). Serum samples from these women were tested for cotinine, a nicotine metabolite.

Main Outcome Measures: Self-reported smoking habits and cotinine levels in ng/mL.

Results: Of 407 women, reporting to be non-smokers, 6% were most likely smokers, and 3% had cotinine levels suggesting exposure to substantial passive smoking. Of 60 women, reporting smoking 1-10 cigarettes per day, 32% were likely to smoke more.

Conclusion: If the true facts about exposure to tobacco smoke are not revealed, a number of women who might benefit from information and support at the antenatal clinic will miss the opportunity of such assistance, resulting in increased risks for both the woman and her fetus.