This experiment was conducted to determine the effect of diabetes on uterine prostanoids production in near-term rats. The incidence of an insulin therapy was also studied. On the 21st day of pregnancy, uterine PGE2, PGF2 alpha and PGI2 levels showed a significant increase (respectively p less than 0.05, p less than 0.01 and p less than 0.05) in diabetic rats compared to controls whereas TxA2 production remained unchanged. The insulin therapy restored PGE2 levels, the most potent stimulatory factor of the myometrial fiber at control values, whereas it enhanced significantly PGI2 concentrations (p less than 0.05) and had no effect on PGF2 alpha production; TxA2 levels remaining always unchanged. It is suggested that the increase in uterine protanolds production during diabetes could induce a myometrial hypertonicity and play a role in the disturbances of the fetal development. The maintenance of PGE2 levels to control values by the insulin therapy might contribute to a normal delivery.