We appreciate Amiel and Blott’s (1) interest in our study (2) and thank them for their helpful discussion. They rightly pointed out that the diagnostic criteria used in Germany at the time of our study had been lower than those of the American Diabetes Association. We were also aware that we treated some women who would have been considered healthy in other countries. To demonstrate that the fetal growth-based approach is also safe for women with a more severe glucose intolerance, we repeated the analysis for a subgroup of women who fulfilled the diagnostic criteria of Carpenter and Coustan (3) (80% of our population). Again, there was no adverse outcome in the ultrasound group. The limitation to women who qualified for gestational diabetes mellitus (GDM) based on Carpenter and Coustan criteria diminished the difference in the rate of insulin therapy. Because of the higher degree of glucose intolerance in these women, more women qualified for insulin therapy in the standard group. We also realized that in the whole population, the rate of women who met the criteria for insulin was higher in the ultrasound than in the standard group. However, this was not because of an unequal representation of fetal macrosomia, as suggested by the authors. The rate of an abdominal circumference of >75th percentile at entry was not different between both groups. It was more likely due to our low diagnostic criteria, which included women with a low degree of glucose intolerance and, therefore, less frequent need of insulin. The low rate of large-for-gestational-age (LGA) babies was an effect of intensive treatment. The studies of Langer et al. (4) and Buchanan et al. (5) demonstrate that a normal LGA rate can be achieved in GDM when we aim for a very tight control.
We were very grateful that Lois Jovanovic’s comment (6) emphasized the aspect of an increased risk for intrauterine growth retardation in some women with GDM. When we discuss treatment strategies for GDM, we always focus on how to reduce neonatal macrosomia. When we did a subanalysis comparing the outcome of women with hyperglycemia but normal fetal growth treated with (standard group) or without (ultrasound group) insulin, we also attempted to determine whether withholding insulin would increase the LGA and cesaerean section rates. We were surprised when we realized the high rate of SGA in the standard group. The overall rate of SGA was similar in both study groups. We did not conclude that the policy of strict glycemic control is harmful for the general population with GDM. We suggested the use of an additional test, the measurement of the fetal abdominal circumference, to decide who will benefit and for whom a tight glucose control might be harmful due to a reduction of the maternal fuel supply to the fetus. Although the differences between the groups were obvious, when we looked at the outcome of the women who were treated differently according to the study protocol, the small sample sizes resulting from the subanalysis impaired our possibilities of an adequate statistical analysis. In the future, we hope to initiate and cooperate in multicenter studies to gather more evidence to prove our results.
