Complications of pregnancy and fetal development.

Although the outcome of pregnancy for women with diabetes mellitus has improved in recent years, the infant of the diabetic mother has an increased risk of major clinical problems, particularly in the early neonatal period. These include birth injury due to macrosomia, neonatal hypoglycemia, respiratory distress syndrome, and serious congenital anomalies. Because of the great difficulties encountered during attempts to investigate these problems in clinical research protocols, there is a continuing need to establish appropriate animal models of the diabetic pregnancy. Studies carried out over the past decade, primarily with chemically-induced diabetes have suggested techniques which might be useful. In general, the choice of the animal to be studied will depend on the hypotheses being addressed. For instance, small animals such as rabbits and rats made diabetic with streptozotocin have been successfully used for investigation of fetal lung development. Furthermore, the rat model has been helpful for evaluation of fetal anomalies associated with maldevelopment of the spine and central nervous system. Larger animals, such as the nonhuman primate, are more appropriate for studying placental function and amniotic fluid composition in diabetic pregnancies. The task group on pregnancy and fetal development recommends that animal models of diabetes mellitus be used for a more extensive hormonal and metabolic characterization of diabetic mothers during pregnancy, for investigation of placental physiology with respect to the transfer of substrates from mother to fetus, for systematic and comprehensive study of mechanisms controlling fetal lung development, and for delineation of the pathophysiology of neonatal hypoglycemia. It is further recommended that animal models of spontaneous diabetes such as the BB/W rat be used in future studies dealing with pregnancy and fetal development. Because females with spontaneous diabetes show reduced conception rates, there is a pressing need to enhance the fertility of these animals in order to intensify studies on fetal development.