[Influence of perinatal factors and sampling methods on thyroid stimulating hormone and thyroid hormone levels in cord blood].

The present study was designed to explore the influence of perinatal factors and sampling methods on fetal pituitary-thyroid axis. The results showed: (1) There was no linear relation between cord serum thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4) and either birth weight or the duration of labor (r = 0.03-0.12, P > 0.05). The mean cord serum TSH, T3 or T4 levels in the fetus delivered with uterotonic agents were no significant difference from those in fetus without these drugs and also there was no significant difference in the mean cord serum TSH, T3 or T4 levels according to the fetus sex (P > 0.05). (2) The mean cord serum TSH level of fetus in vacuum extraction group was significantly higher than that of fetus in normal vaginal delivery or caesarean section group (P < 0.01). However, the mean TSH levels of neonates on day 3-5 in heel blood spotted filter paper were no significant differences among the three groups (P > 0.05). (3) The mixed cord blood TSH level related quite well to the TSH level obtained from heel blood on day 3-5, or cord venous serum samples (r = 0.67-0.84, P < 0.01). Our results suggest that measuring cord blood TSH level might be a feasible alternative method for neonatal congenital hypothyroidism screening.