Effects of maternal hypoglycemia on fetal eye and skeleton development in rats

The relationship between insulin-induced maternal hypoglycemia and teratogenicity was investigated in detail. We injected 4 different forms of insulin (insulin human, aspart, glargine, and detemir) subcutaneously at 1 or 2 dose levels to Sprague-Dawley rats from Days 6 to 11 of pregnancy, measured blood glucose levels, and conducted fetal examination. In the insulin human and aspart (low dose) groups, while severe hypoglycemia (approximately 50mg/dL) was seen, it lasted only 6h and no fetal anomalies were observed. Fetal axial skeleton anomalies were observed in the aspart (high dose) group, which exhibited intermediate-duration of severe hypoglycemia (9h). Eye and axial skeleton anomalies were observed in the glargine and detemir groups, which exhibited continuous severe hypoglycemia (≥9h). These results revealed that insulin-induced maternal hypoglycemia caused fetal eye and skeleton anomalies and the causative key factors were duration of maternal severe hypoglycemia.