A Longitudinal Analysis of Maternal Serum Insulin-Like Growth Factor I (IGF-I) and Total and Nonphosphorylated IGF-Binding Protein-1 in Human Pregnancies Complicated by Intrauterine Growth Restriction

In cord blood and late gestation maternal serum, IGF-I is positively correlated with birth weight, whereas IGF-binding protein-1 (IGFBP-1) is inversely correlated with birth weight. Our goal was to determine whether maternal serum or amniotic fluid concentrations of IGF-I, IGFBP-1, or nonphosphorylated IGFBP-1 (npIGFBP-1) in early gestation predict later fetal growth abnormalities. Maternal serum was collected prospectively across gestation (5–40 wk) from 749 pregnant subjects. Amniotic fluid was collected after amniocentesis during wk 15–26 from 207 subjects. We compared median serum concentrations of IGF-I, IGFBP-1, and npIGFBP-1 in 38 subjects who delivered growth-restricted infants with the control group of 236 subjects with normal weight infants for each gestational age grouping, wk 5–12, 13–23, and 24–34. In the control group median IGF-I concentrations were 14.8, 11, and 15.6 nmol/liter for wk 5–12, 13–23, and 24–34, respectively, compared with 13.7, 14.3, and 10.6 nmol/liter in the intrauterine growth restriction (IUGR) group. Median IGFBP-1 concentrations were 8.5, 30.4, and 24.4 nmol/liter, respectively, in controls, compared with 11.4, 28.6, and 25.5 nmol/liter in the IUGR group. Median npIGFBP-1 concentrations were 6.9, 22, and 17.4 nmol/liter, respectively, in controls, compared with 5.0, 32.1, and 24.2 nmol/liter in the IUGR group. In the control group the median amniotic fluid IGFBP-1 level was 13,160 nmol/liter, and the median npIGFBP-1 level was 15,970 nmol/liter; in the IUGR group these levels were 13,440 and 18,440 nmol/liter, respectively. No clinically useful differences were found between the IUGR and control groups. Our results do not support the use of maternal serum IGF-I or IGFBP-1 or amniotic fluid IGFBP-1 or npIGFBP-1 early in gestation to predict later fetal growth restriction.