Fetal growth and development is dependent upon various growth factors such as glucose, insulin, HGH and IGF-I. These growth factors were measured in maternal serum (MS), amniotic fluid (AF) and umbilical venous serum (UV) in late gestation in normal, insulin dependent diabetic pregnancies (IDDM) and in pregnancies complicated with intrauterine growth retardation (IUGR). The UV glucose values of 1.9 +/- 0.9 mmol/L and UV insulin values of 8.0 +/- 1.8 mU/L were the lowest in IUGR pregnancies, and the highest were in UV serum from IDDM pregnancies, and the difference was statistically significant for this two groups. IGF-I values in UV indicated that there was significant difference in IGF-I concentrations when both, IUGR and IDDM groups were compared to the controls. There was a parallel shift in AF and MS glucose and insulin concentration as birthweight increased. The highest IGF-I values of 7.2 +/- 9.6 mumol/L in AF and MS were found in pregnancies with infants whose birthweight was 3500 grams and greater. Infants from pregnancies complicated with IUGR and IGF-I low values of 0.6 +/- 1.2 mumol/L in AF. HGH concentrations of 15.6 +/- 9.4 micrograms/L in UV were observed in IDDM pregnancies and significantly lower than the values in IUGR and normal pregnancies. HGH umbilical venous values decreased with duration of pregnancy and with increase in fetal size. The high HGH concentrations in the fetus and its dramatic fall after parturition, and the obtained negative correlation between HGH and IGF-I in umbilical vein may exhibit the maturation of the hypothalamic-growth hormone-IGF-I axis. It seems likely that changes in maternal serum, umbilical venous and amniotic fluid insulin-like growth factor I influence birthweight in normal and IUGR infants and in those of diabetic mothers.