C-peptide, insulin-like growth factors I and II, and insulin-like growth factor binding protein-1 in umbilical cord serum: correlations with birth weight.
OBJECTIVE
Our purpose was to determine the correlation between birth weight and hormones or growth factors believed to be involved in fetal growth: insulin, insulin-like growth factors I and II, and insulin-like growth factor binding protein-1.


METHODS
Five hundred thirty-eight cord serum samples were analyzed for insulin-like growth factor-I, insulin-like growth factor-II, C-peptide, and insulin-like growth factor binding protein-1 by immunoassay. Samples included all gestational ages in the third trimester and a large range of birth weights.


RESULTS
Cord serum insulin-like growth factor-I concentrations increased until 39 weeks (+84% from 28 to 29 weeks), followed by a 21% decline at 41 weeks. Insulin-like growth factor-I levels were decreased by 40% in small-for-gestational-age (< 10th percentile) newborns and were increased by 28% in large-for-gestational-age (> 90th percentile) newborns in the absence of diabetes. Insulin-like growth factor-I levels were best correlated with birth weight (R = 0.48, p < 0.001). Cord serum insulin-like growth factor-II concentrations were sixfold to tenfold higher than those of insulin-like growth factor-I and were 8% to 10% (p < 0.001) higher in large-for-gestational-age than in average-weight and small-for-gestational-age newborns. Cord serum C-peptide concentrations were 28% and 34% higher in large-for-gestational-age than in average-for-gestational-age and small-for-gestational-age newborns, respectively. Insulin-like growth factor binding protein-1 levels were increased in preterm average-for-gestational-age and in term small-for-gestational-age newborns compared with term average-for-gestational-age newborns and showed a negative correlation with birth weight (R = -0.43, n = 131, p < 0.001). Insulin-like growth factor binding protein-1 was not correlated with C-peptide concentrations.


CONCLUSIONS
Insulin-like growth factors I and II and insulin are all related to fetal growth and weight gain, and insulin-like growth factor-I correlates best with birth weight. Insulin is mainly related to fetal overgrowth (macrosomia). Insulin-like growth factor binding protein-1 may be a growth inhibitor in the fetus.
Verhaeghe
J
J
Department of Obstetrics and Gynecology, Katholieke Universiteit Leuven, Belgium.
Van Bree
R
R
Van Herck
E
E
Laureys
J
J
Bouillon
R
R
Van Assche
F A
FA
D000328:Adult; D001724:Birth Weight; D002096:C-Peptide / Q000097:blood*; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008297:Male
D002096:C-Peptide; D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II