Somatomedin in newborns and the relationship to human chorionic somatotropin and fetal growth.

The significance of somatomedin A (SM) and human chorionic somatomammotropin (HCS) in fetal growth was examined. SM, determined by chick embryo assay, was studied during the last trimester of pregnancy, in maternal serum and cord blood at term and in a group of normal newborns in the first week of life. Furthermore a group newborns of diabetic mothers was studied in the first or second day of life. HCS was measured in maternal serum and in cord blood at term. In amniotic fluid inhibitory factors caused a low SM activity as measured by the bioassay. The following results were obtained: 1) Normal values of SM in the last trimester with a decline at term were found in 3 normal primigravidae. 2) The mean levels of SM in 22 mothers and their offspring were decreased. The difference between the two values was significant, but a positive correlation was found between the maternally related pairs of SM values. Moreover, a positive correlation was found between maternal SM, birth weight and length. HCS was not correlated to above-mentioned parameters, but there was positive correlation between placental weight and birth weight. 3) In 6 newborns during the first 5 days SM rose from very low values to normal values found in infants in their first year. 4) The mean value of SM in ten newborns of diabetic mothers was not significantly different from the mean value of control group. The results do not exclude the possibility of a transplacental transport of SM and the positive correlation between SM levels and birth weight found in this investigation supports the concept that SM plays an important role in fetal growth.