Effects of Tobacco Exposure on Maternal Thyroid Function During the First Trimester of Pregnancy

Abstract Aim This study aimed to assess the deleterious effects of tobacco exposure on maternal thyroid function and investigate its relationship to subclinical hypothyroidism in pregnant women during the first trimester. Subjects and Method A comparison of maternal thyroid function was made on 45 smokers, who composed the study group, and 72 non-smokers, pregnant women, which constituted the control group. After determining smokers by questionnaire, carbon monoxide (CO) levels were measured and recorded in the expiratory air of the participants in both groups, and the exposure of smokers was objectively confirmed. Results Smoking and non-smoking pregnant women were similar in terms of body mass index (BMI). Maternal serum TSH levels were lower in the smoking group compared to the non-smoker group (1.48 ± 0.12 mIU/L versus 1.72 ± 0.13 mIU/L), but the difference was not statistically significant (p = 0.239). Even though the rate of subclinical hypothyroidism was 8.9% in the smoking group, it was approximately 19.4% in the non-smoker group (p = 0.187). Conclusion This study proved that lower serum TSH levels were encountered in smokers during pregnancy, but there was no statistically significant difference between the groups.