Aim This study aimed to assess the effect 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,
who constituted the control group. After determining smokers by questionnaire,
carbon monoxide (CO) levels in the expiratory air of the participants in both
groups were measured and recorded, and the smokers’ exposure was
objectively confirmed.
Results Smoking and non-smoking pregnant women were similar regarding body
mass index (BMI). While the TSH and fT4 levels were respectively 1.48
mlU/L and 11.43 pmol/L in pregnant women who smoked, that ratio
changed to 1.72 mlU/L and 11.17 pmol/L in the
non-smokers’ group. But the differences between the groups were not
statistically significant (p=0.239, p=0.179). Even though the
rate of subclinical hypothyroidism was 8.9% in the smoking group, it was
approximately 19.4% in the non-smoker group; the difference was not
statistically significant (p=0.187).
Conclusion This study proved that there is no statistically significant
difference between maternal serum TSH and fT4 levels and the rate of subclinical
hypothyroidism in smokers during pregnancy in the first trimester.