Specific binding of 125I-human epidermal growth factor (hEGF) to homogenates of term human placentas and fetal membranes from normal and appropriate for gestational age (N = 20), intrauterine growth retarded (N = 9), twin (N = 11), White class A/B diabetic (N = 12), and large for gestational age (N = 13) pregnancies was measured. In all pregnancy states, placentas bound approximately four times more 125I-hEGF than did fetal membranes (P less than 0.001). There was no significant difference in 125I-hEGF binding to fetal membranes from the various pregnancy states (P greater than 0.05). 125I-hEGF specific binding to placentas from intrauterine growth retarded or twin pregnancies was significantly greater compared with placentas from normal and appropriate for gestational age pregnancies (P less than 0.05). The binding to placentas from pregnancies complicated by White class A/B diabetes or large for gestational age infants, on the other hand, was not significantly different from that to placentas from normal and appropriate for gestational age pregnancies. 125I-hEGF specific binding did not differ between placentas from intrauterine growth retarded or twin pregnancies (P greater than 0.05). Placental and fetal membrane 125I-hEGF binding did not vary with fetal sex, maternal race, placental weight, or gestational age between 37 to 42 weeks (P greater than 0.05). Placental but not fetal membrane 125I-hEGF binding increased with increasing infant weight when appropriate for gestational age and large for gestational age infants were included (P less than 0.05, r = 0.38, N = 32) but not for intrauterine growth retarded, appropriate for gestational age, or large for gestational age infants alone.