Smoking Exposure in Early Pregnancy and Adverse Pregnancy Outcomes: Usefulness of Urinary Tobacco-Specific Nitrosamine Metabolite 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol Levels

Objectives: The aim was to investigate the effect of -maternal smoking exposure assessed by urinary tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-a1-butanol (NNAL) with adverse pregnancy outcomes. Methods: A total of 251 pregnant women were recruited. Urinary cotinine and NNAL were measured. Participants' sociodemographics were obtained by questionnaire and pregnancy outcomes were collected by charts review after delivery. Results: The prevalence of smoking was 8.4% (21 of 249), 1.2% (3 of 241), and 3.7% (9 of 241) in pregnant women according to questionnaire, cotinine, and NNAL, respectively. As compared with questionnaire positivity and cotinine levels, women with positive NNAL were independent determinants for spontaneous abortion (adjusted OR 12.357, 95% CI 2.053-74.368), preterm birth (adjusted OR 22.239, 95% CI 3.737-132.357), and small for gestational age (adjusted OR 6.915, 95% CI 1.385-34.524). Conclusions: Urinary NNAL might be a useful biomarker in detection of maternal smoking status in association with adverse pregnancy outcomes. Use of this marker in preconception and pregnancy counselling before planning pregnancy may allow prevention of several adverse pregnancy outcomes.