Somatomedin bioactivity in serum and amniotic fluid during pregnancy.

Somatomedin bioactivity (SMA) in maternal serum, as measured by hypophysectomized rat cartilage assays, was low during early and late pregnancy but was similar to normal nonpregnant control levels near 28 weeks and at term pregnancy. At term, the mean level of SMA in cord serum was significantly less than in maternal serum, and greater than in amniotic fluid. The mean level of SMA in amniotic fluid was higher at term than in early pregnancy. No significant correlation was noted between SMA levels in amniotic fluid, maternal serum or cord serum, or between the SMA levels in these samples and the usual amniotic fluid parameters used as indices of fetal maturity.