The effect of tobacco exposure on maternal and fetal thyroid function

Abstract: Objective: To determine the effect of smoking on maternal and fetal thyroid function. Study design: This prospective cohort study involved healthy women undergoing elective cesarean section for term singleton infants. Maternal and fetal thyroid indices were compared between smokers (n =21) and non-smokers (n =83). Results: Maternal thyrotropin (TSH) concentrations were significantly lower in smokers than non-smokers (1.75mIU/L versus 2.15mIU/L, respectively, p =0.007), with similar free thyroxine (FT4) concentrations (9.59pmol/L versus 9.56pmol/L, p =0.755). For women who smoked, the correlation between the average number of cigarettes smoked per day and maternal TSH concentrations was −0.427, p =0.054. Infants of smokers and non-smokers had similar umbilical TSH (5.43mIU/L versus 5.82mIU/L, p =0.124) and FT4 concentrations (13.06pmol/L versus 13.57pmol/L, p =0.049). Conclusion: We demonstrated for the first time that women who smoke during pregnancy have significantly lower TSH concentrations than non-smokers. [Copyright &y& Elsevier]