RESUMO
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). The study sample included 129 infants 34-36 weeks' gestation. There were no differences in total T4 between infants born by cesarean or vaginal delivery (p=0.18), or between those requiring respiratory support compared to infants not requiring respiratory support (p=0.09). At Time 2, 93% of the study population had a total T4 below one standard error of the reference laboratory mean. In our study sample, despite many infants having a low total T4, there was no association between total T4 levels, respiratory support, or mode of delivery.