title: Maternal insulin-like growth factor-I levels (IGF-I) reflect placental mass and neonatal fat mass.
abstract: OBJECTIVE
  This study was undertaken to test the null hypothesis that serial changes in maternal insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding-protein-1 (IGFBP-1) levels during pregnancy do not reflect differences in either corrected birth weight or placental mass at term. Study design Serial blood samples were obtained before pregnancy and at 8, 16, 24, 32, and 38 weeks from 56 healthy women enrolled in various exercise training regimens. Maternal, placental, and fetal morphometric parameters were monitored throughout. Enzyme-linking immunosorbent assays were used to determine IGF-I and IGFBP-1 levels.
  
  
  RESULTS
  IGF-I and IGFBP-1 levels varied widely among the subjects at all time points, but there was a consistent fall in IGF-I levels in early pregnancy, followed by a rapid increase between 16 and 36 weeks' gestation, whereas IGFBP-1 levels rose in the first 16 weeks and were unchanged thereafter. The strongest linear correlations with morphometric outcome were between the increase in maternal IGF-I levels from 16 to 32 weeks and corrected birth weight (r(2)=0.27), neonatal fat mass (r(2)=0.65), and placental mass at term (r(2)=0.50). These were improved when maternal glucose level was included in a stepwise regression analysis (r(2)=0.50-0.70).
  
  
  CONCLUSIONS
  There is a robust relationship among the rate of increase in individual maternal IGF-I levels after 16 weeks, placental mass, and neonatal fat mass. This does not imply causality but does indicate that midpregnancy changes in IGF-I levels may be a valuable marker for anomalous fetal growth.
authors.affiliation: Department of Reproductive Biology and Obstetrics and Gynecology and the Schwartz Center for Metabolism and Nutrition, Case Western Reserve University at MetroHealth Medical Center Cleveland, Ohio, USA. jfclapp@metrohealth.org
authors.forename: James F
authors.initials: JF
authors.lastname: Clapp
authors.forename: Stephanie
authors.initials: S
authors.lastname: Schmidt
authors.forename: Aditi
authors.initials: A
authors.lastname: Paranjape
authors.forename: Beth
authors.initials: B
authors.lastname: Lopez
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D001786:Blood Glucose / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009929:Organ Size; D010920:Placenta / Q000033:anatomy & histology*; D011247:Pregnancy / Q000097:blood*
chemical_list: D001786:Blood Glucose; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I