Neonatal thyrotrophin and mode of delivery.

This study was performed to assess the association between labour and the mode of delivery with the umbilical cord plasma thyroxine (T4) and thyroid-stimulating hormone (TSH) concentrations in full-term uncomplicated pregnancies delivered in our hospital. Babies born vaginally had statistically significantly higher umbilical cord plasma TSH but similar T4 concentrations than babies born by caesarean section. Labour was not associated with either higher TSH or T4 concentrations. All the babies with an elevated TSH concentration (greater than 20 miu/l) were born vaginally. Our findings indicate that the mode of delivery should be taken into consideration in the interpretation of umbilical cord plasma TSH results.