In the present study, we have shown that both maternal prepregnancy weight and weight gain during pregnancy in excess of the IOM recommendations appear to be independent and important risk factors for the development of macrosomia in women with GDM. Although earlier studies have demonstrated similar associations of maternal BMI and excess gestational weight gain to increased birthweight in normal pregnant women, (1316 to 192627) to our knowledge, our results are the first to demonstrate such a link in women with GDM