Rapid overgrowth of a fetus after interruption of insulin therapy in a diabetic woman

We experienced a case of fetal overgrowth probably due to maternal hyperglycemia following the interruption of insulin therapy in a woman with gestational diabetes mellitus (GDM), probably undiagnosed type 2 diabetes mellitus. A 27-year-old Japanese woman was referred to our center because of GDM at 15 weeks of gestation. During the course of her educational admission, diet control and insulin therapy resulted in favorable blood sugar levels and she was discharged at 17 weeks of gestation. During these periods, fetal growth remained below average at between -1 and -1.5 S.D. After a check-up in the 29th week, she failed to appear for any further appointments. After the onset of labor, at 38 weeks of gestation, she suddenly consulted her former physician who delivered a baby weighing 4852 g by cesarean section on the 38th week. A noteworthy point in this case is the growth curve of the fetus. Even if rapid overgrowth is assumed, starting after the time of interruption of insulin at 30 weeks of gestation, fetal weight gain appears to be about 400 g per week, suggesting a weight increase at twice the normal rate. This case prompted us to keep in mind that rigid glycemic control will prevent the development of fetal macrosomia in diabetic pregnant women.