Serum levels of insulin-like growth factor-binding protein-3 in normal pregnancy.

The aim of this study was to investigate circulating levels of insulin-like growth factor-binding protein-3 (IGFBP-3) in women with normal pregnancy. A total of 468 pregnant women at various gestational ages and 30 non-pregnant females were recruited in this study. Serum concentration of IGFBP-3 was determined by radioimmunoassay. Maternal serum levels of IGFBP-3 increased as pregnancy progressed. The concentration of IGFBP-3 in pregnancy serum was positively associated with the gestational age. The mean values of circulating IGFBP-3 in the second and third trimesters of pregnancy were higher than those in the first trimester of pregnancy and in non-pregnant females. In addition, there was a highly significant correlation between IGFBP-3 and IGF-I in pregnancy serum. We conclude that, during pregnancy, IGFBP-3 appears to be the principal binding protein for circulating IGF-I and may be involved in the regulation of fetal growth.