Serum T3 and T4 levels at birth in infants 30-40 weeks gestation

ABSTRACT

This study included thirty healthy newborn infants whose estimated gestational ages ranged from 30-44 weeks. They were classified into 3 groups [1] 10 pre-term infants with gestational ages ranging from 30-36 weeks and body weights 1800-2450 gms, [2] 10 full term infants with gestational ages ranging from 38-40 weeks and body weights 2750-3200 gms and [3] Post-term infants with gestational ages ranging from 42-44 weeks and body weights 3000-4000 gms. The mean cord serum T3 values in the three groups were 39.9 +/- 11.15 ng%, 44.9 +/- 13.788 ng% and 66 +/- 3.528 ng% respectively. There was a statistical significant difference between group 1 and 3, group 2 and 3 while there was no significance between group 1 and 2 demonstrating increases of T3 values with increasing both gestational age and body weight. The mean cord serum T4 values in the 3 groups were 10.51 ug%. 10.19 ug% and 9.3 ug% respectively. The difference was statistically insignificant between the three groups. In evaluating T3 and T4 results in a population of low birth weight infants, normative data from full term babies can not be used as screening programs for congenital hypothyroidism. The high percentage of false positives found in premature infants might be decreased by the use of normal values adjusted according to gestational age