Somatomedin-C levels related to gestational age, birth weight and day of life.

Capillary blood samples on filter paper were assayed by means of an RIA method (Kit Nichols Institute USA) from 1096 newborns divided into full term, preterm and small-for-date infants. The somatomedin-C (Sm-C) mean value, which did not differ in the three groups, was 0.15 +/- 0.09 IU/ml. One hundred and ten (10%) showed Sm-C disc values less than or equal to 0.075 IU/ml, the minimum value measurable by our method. The day of life and birth weight had a significant influence on Sm-C levels. Gestational age did not have any significant effect. No significant interaction was found among the parameters considered. All the groups presented a progressive increase of Sm-C. Unlike preterm and small-for-date infants, in full term infants the latter increase seemed already to be evident from 5th day of life and reached higher levels from the 7th day of life onwards. In conclusion, Sm-C rates were reduced in the neonatal phase of life, but showed a tendency to rise later.