Study of Effect of Passive Smoking on Level of Infants’ Thyroid Hormones and Anthropometric Indices by Women’s Self-Report and Urinary Cotinine Level at Delivery

Introduction: Passive smoking in pregnancy has severe maternal and fetal effects and it is argued that smoking and low birth weight are associated. Also smoking could affect thyroid gland’s function. This study was aimed to study the effect of passive smoking on level of maternal thyroid hormones and infants’ anthropometric indices by women’s self-report and urinary cotinine level at delivery.Materials & Methods: This historical, cohort study investigated 108 pregnant women who were assigned to two groups of 54 each, randomly with equal probability, exposed and unexposed to cigarette smoke. In this study, the data were collected by filling out the questionnaires of lifestyle and passive smoking through interview. Also, infants’ head circumference (HC), height, and weight, and level of TSH, T4, and T3 in infants’ serum sample, and level of maternal urinary cotinine were investigated. Results: Findings indicated that T3 and T4 levels increased significantly in the infants of the women with passive smoking by both the women’s self-report and maternal urinary cotinine level. Infants’ TSH level exhibited no statistically significant change. There was no significant difference in infants’ height and HC between the two groups, but weight decreased significantly in the infants of the women with passive smoking.Conclusion: The findings demonstrate that passive smoking results in increased maternal serum level of T3 and T4 hormones and weight decreased significantly in the infants. Therefore, training the hazards and harms of smoking during pregnancy to women, and developing and implementing interventions to decrease cigarette smoking and hence to promote maternal, infants’, and families’ health is required