The effect of the mode of delivery on neonatal thyroid function.

Background: We aimed to investigate the effect of the mode of delivery and the type of anesthesia on postnatal thyroxine (T4), free T4 (f-T4) and thyroid-stimulating hormone (TSH) in a large number of healthy full-term neonates.

Methods: Serum samples for T4, TSH and f-T4 were drawn from neonates at the time of discharge (postnatal days 1-7) in a pilot thyroid-screening program. Six hundred and thirty-eight neonates were grouped as: vaginal delivery (VD; 332), elective cesarean section (elective C/S; 252) and emergency cesarean section (emergency C/S; 54).