An immunohistochemical study of type I insulin-like growth factor receptors in the placentae of pregnancies with appropriately grown or growth restricted fetuses

Insulin-like growth factors (IGFs) and their receptors in the fetus are ess ential for growth and postnatal survival but the role of maternal IGFs is l ess well understood. Animal and in vitro evidence suggests that maternal IG F-I may have important effects on placental function. Recent work in humans suggests that although there is no relationship between maternal serum IGF -I and normal fetal growth, levels are low in pregnancies complicated by fe tal growth restriction due to placental dysfunction. A prospective and obse rvational study was undertaken of the distribution and concentration of pla cental type I IGF receptors (IGF-IR) in women with small for gestational ag e (n=26) or appropriately grown (n=14) fetuses. Women were scanned biweekly from 24 weeks to delivery and cases (birthweight <5th centile) were assign ed to two groups: 'fetal growth restriction' (FGR; umbilical artery pulsati lity index [UAPI] >+2 s.d.; n=16) and 'normal small for gestational age' (S GA; normal UAPI, growth velocity and amniotic fluid; n = 10). Immunohistoch emistry of the IGF-IR was performed on formol saline-fixed placental biopsi es obtained at delivery. In control pregnancies IGF-IR were present in vill ous endothelium and stroma, trophoblast and decidua and their distribution and density were unchanged in both SGA and FGR pregnancies. We hypothesize that a therapeutic elevation of maternal IGF-I in FGR pregnancy might lead to enhanced placental function and so fetal growth. Our findings of normal localization and density of placental IGF-IR in FGR encourage us to extend our work to look at the effects of maternal IGF-I on the transport of gluco se and amino acids. (C) 1999 W. B. Saunders Company Ltd.