NSILA AND FETAL GROWTH

Employing a sensitive competitive protein binding assay for NSILA (non-suppressible insulin-like activity), circulating levels of this somatomedin (SM) have been measured throughout pregnancy, at parturition, and in foetal and newborn sera. Acid-dissociable serum NSILA (mean ± SEM) in 57 women was significantly higher during pregnancy (1106 ± 46 μU/ml), than in 11 adult non-pregnant control subjects (844 ± 22 μU/ml), but not correlated with week of gestation or with serum growth hormone (GH) or cortisol levels. At parturition, the NSILA concentration in 28 cord sera (598 ± 38 μU/ml) was significantly less than in the corresponding maternal sera (1039 ± 63 μU/ml). The NSILA levels in 23 premature newborns (370 ± 20 μU/ml) and 8 small-for-gestational-age newborns (310 ± 46 μU/ml) were significantly less than in 33 term newborns (494 ± 18 μU/ml). Serum NSILA in 56 term and premature newborns exhibited a significant positive correlation both with gestational age and birth weight but not with serum GH or cortisol levels. These data suggest that the maternal-foetal growth-promoting system is a highly complex one in which NSILA levels both in maternal and foetal circulations appear to be under multifactorial control.