Smoking during pregnancy--effects on the fetal thyroid function

Area of Science:

• Endocrinology
• Neonatalogy
• Public Health

Background:

• Maternal smoking during pregnancy is a significant risk factor for adverse neonatal outcomes.
• The impact of maternal smoking on fetal thyroid function and its relation to growth retardation requires further elucidation.

Purpose of the Study:

• To investigate the association between maternal smoking and cord serum thyroid hormone levels in term infants.
• To explore the potential role of fetal thyroid function in mediating growth retardation observed in infants of smoking mothers.

Main Methods:

• Comparison of birthweights and cord serum thyroid-stimulating hormone (TSH), thyroxine (T4), and free thyroxine index (FT4I) between infants of mothers who smoked heavily during pregnancy and non-smoking mothers.
• Statistical analysis to determine significant differences between the groups.

Main Results:

• Infants of mothers smoking ≥10 cigarettes daily had significantly lower birthweights compared to controls (p < 0.05).
• Cord serum TSH was significantly decreased, and the FT4I/TSH ratio was significantly increased in the smoking group (p < 0.05).
• Cord serum T4 and FT4I showed a trend towards being higher in the smoking group (0.05 < p < 0.10).

Conclusions:

• Infants born to mothers who smoke heavily during pregnancy may exhibit signs of fetal thyroid gland hyperfunction at birth.
• This thyroid hyperfunction, potentially leading to increased metabolic rate and oxygen consumption, may be a contributing factor to fetal growth retardation associated with maternal smoking.