It does not exclude the possibility that glucose intolerance may have antedated the pregnancy. Mellitus recommended that all pregnant women be screened for gestational diabetes, with a 50g oral glucose load followed by a glucose determination 1 hour later 4 . This test is generally performed at 24 - 28 weeks gestation. Macrosomia in these infants is characterized by specific organomegaly with increases in fat and muscle mass specifically in the fetal trunk and shoulders. Brain growth is usually not altered therefore the head circumference is usually normal.
Serial ultrasound is an excellent modality to evaluate macrosomia.
The abdominal circumference measurement is probably the most reliable sonographic parameter for the detection of macrosomia in the third trimester. In a study by Landon et al of 97 diabetic women, who had at least 3 ultrasound studies in the third trimester of pregnancy, accelerated abdominal circumference growth was found 5 . Landon et al performed a second prospective study of fetal humeral soft tissue thickness measurements in pregnancy complicated by GDM to determine whether this parameter could predict fetal size 2 . Sonograms were performed during the third trimester in 93 women with GDM and 198 non diabetic pregnancies. This study also revealed accelerated growth beginning at 31 weeks gestation.