Insulin receptors in human placenta in relation to fetal weight and gestational age.

Insulin receptors were studied in human placentas from 26 wk to term, according to fetal and placental weight. Insulin-binding studies were performed in purified membranes with monoiodoinsulin biologically active. We found a marked decrease in receptor number in placentas corresponding to small for gestational age infants (S.G.A.) in relation to preterm and full-term adequate for gestational age (A.G.A.). Maximal insulin binding in human placentas was reached before 26 wk of gestation.