Thyroid function in late preterm infants in relation to mode of delivery and respiratory support.

The relationship between thyroid function, mode of delivery, and illness in infants 34-36 weeks' gestation has not been well studied. We hypothesized that infants born by cesarean delivery and those with increased illness would have a reduction in thyroxine (T4) following birth. Total T4 and thyroid-stimulating hormone were obtained at birth (Time 1) and between days 2 and 5 (Time 2).