Insulin-like growth factor-binding protein-1 in umbilical artery and vein of term fetuses with signs suggestive of distress during labor

Insulin-like growth factor-binding protein-1 (IGFBP-1) is believed to be an inhibitory factor for fetal growth. The regulation of IGFBP-1 secretion in the fetus is uncertain, although insulin and oxygen tension (PO,) and satu ration are thought to play a role. We studied IGFBP-1 levels in umbilical c ord artery (UA) and vein (UV) of 98 singleton fetuses at term with clinical signs of distress during labor, i.e. meconium-stained liquor or/and an abn ormal fetal heart rate tracing. Blood gas values and serum C-peptide and IG FBP-1 concentrations were measured in both UA and UV. Twenty-five fetuses h ad an UA pH <7.20. The concentrations of IGFBP-1 were similar in UA and UV and were highly correlated (r=0.98). IGFBP-1 levels were inversely correlat ed with birth weight, with increased concentrations in small-for-gestationa l age fetuses (less than or equal to 10th weight percentile). IGFBP-1 level s were negatively correlated with C-peptide concentrations, and remained so after correction for birth weight (r = - 0.37 for both UA and LW; P <0.001 ); more specifically, IGFBP-1 levels were increased in the lowest C-peptide quartile (<0.23 nmol/l) compared with the other quartiles. In addition, IG FBP-1 levels were inversely correlated with PO2 values (r= -0.39 in UA and r= -0.34 in UV; P <0.001); quartiles of UA and UV PO, showed a gradual incr ease in IGFBP-1 concentrations with lower PO2 values. A regression model wi th C-peptide and PO2 Values as independent variables predicted IGFBP-1 conc entrations (R-2 of model was 0.25 and 0.22 for UA and UV respectively; P <0 .001). Other blood gas values (pH, PCO2, HCO, - and base deficit) did not c orrelate with IGFBP-1 levels. The data of this study indicate that serum IG FBP-1 levels in term fetuses are determined by both insulin and PO2 levels, and suggest that acute hypoxemia stimulates IGFBP-1 secretion in the fetus .