The interrelations between three placental hormones (oestradiol, progesterone and hPL), maternal glucose metabolism, maternal anthropometry and fetal growth were studied in a sample of 52 carefully selected pregnant women. A relation was found between infant birthweight and both fasting blood glucose and t1/2 of glucose of an intravenous glucose tolerance test at week 37 of pregnancy. The serum concentrations of the placental hormones were not significantly related to the glucose variables. The correlation between birthweight and the maternal levels of hPL in late pregnancy (r = 0.60) persisted when fasting blood glucose and t1/2 of glucose were taken into account. Maternal fat mass was found to explain more of the variation in basal insulin levels around week 37 than did the placental hormones.