Significance of screening tests for gestational diabetes mellitus:identification of possible maternal-fetal complications rather than macrosomia

In the last few years, the glycemic thresholds for the diagnosis of gestational diabetes mellitus have been lowered. Therefore, the gestational diabetes mellitus is diagnosed more and more often. Especially, we are able to detect the mild cases of gestational diabetes mellitus. Nevertheless it is not well understood whereas these mild cases of gestational diabetes could mean much rate of adverse outcomes of pregnancy and delivery, with special regard to fetal macrosomia. So we reviewed our data about fetal macrosomia between 1990 and 1998 and compared them with others in literature, to evaluate if the gestational diabetes mild cases diagnosed by the lower glycemic thresholds may be helpful for management of pregnancy. Fetal macrosomia rate was 6.48%, but 63.8% of these macrosomic babies was found in women who resulted healthy after a pathological oral 50 g glucose challenge test and normal oral 100 g glucose tolerance test (OGTT), in women affected by a gestational diabetes mellitus after a 100 g OGTT and in women who had a pregestational diabetes. We used the Carpenter and Coustan thresholds for 100 g OGTT for the diagnosis of gestational diabetes mellitus and a 1 hour 140 mg% threshold after 50 g oral glucose load test. Apart from fetal macrosomia, no other adverse outcomes of pregnancy and delivery was found. These macrosomic babies were born spontaneously, with no differences with controls. We conclude that insuline resistance may explain both abnormal glucose value after any OGTT and fetal macrosomia. The utility to detect any low state of insuline resistance may be anywhere questionable because, in these cases, macrosomic babies may born with no complications.