Amniotic fluid reactivity detected by somatomedin C radioreceptor assay: correlation with growth hormone, prolactin and fetal renal maturation.

Amniotic fluid was assayed by a radioreceptor assay utilizing 125I-somatomedin C and placental membranes. Growth hormone and prolactin levels were measured by radioimmunoassay at different gestational ages (8-41 weeks). Somatomedin receptor activity, growth hormone, and prolactin reached high levels during early gestation (8-26 weeks) displaying different patterns of appearance which reflect fetal serum levels of these hormones. After 26 weeks gestation all these hormones decreased in concentration. This decrease showed a strong correlation with fetal renal maturation as measured by amniotic fluid creatinine levels.