Maternal serum insulin-like growth factor binding protein-2 and-3 and fetal growth

This was a prospective observational study of maternal insulin-like growth factor binding protein-2 and -3 and fetal growth in 141 pregnant women afte r 24 weeks gestation who were scanned and venesected fortnightly. Cases (bi rthweight <5th centile) were sub-divided into those with growth restriction due to placental dysfunction (n = 25) and normal small (n = 27) and there were 89 normally grown controls. Maternal binding protein-3 was measured by radioimmunoassay and the overall pattern of the binding proteins and their proteolytic modifications were assessed by Western ligand blotting and imm unoblotting followed by densitometric analysis. In controls, there was no c orrelation between binding protein-3 and birthweight, and binding protein-3 was elevated in the normal small but not the placental dysfunction group. Complete proteolysis of the 40 kDa doublet of binding protein-3 was observe d in all pregnancies. Maternal serum binding protein-2 concentrations were unchanged in normal pregnancy compared to non-pregnant controls but elevate d in the growth-restricted group and in all pregnancies binding protein-2 w as predominantly present as a 14 kDa proteolysed fragment. These results su ggest that compensatory changes in binding protein-2 and -3 or their proteo lysis do not increase bioavailability and so do not confound the low matern al insulin-like growth factor-I in growth restricted pregnancies.