Background: Ultrasound assessment of abdominal circumference early in the third trimester had been proposed to introduce insulin therapy in order to prevent fetal overgrowth in women with mild gestational diabetes mellitus. The purpose of this study was to investigate adequate weeks gestation timing for testing this parameter.
Methods: One hundred and forty-one women were included in a randomized trial. Seventy-three women were evaluated at both 28 and 32 weeks gestation whereas 68 women were investigated only at 32 weeks gestation. In both groups, insulin therapy was promptly started when abdominal circumference exceeded the 75th percentile. Macrosomic rates were compared using the Fisher's exact test.
Results: Twenty-nine women whose fetal abdominal circumference exceeded the 75th percentile were considered eligible for insulin therapy. In this group, we observed a statistically significant increase in the percentage of macrosomic infants born from women whose ultrasound abdominal circumference assessment was performed only at 32 weeks gestation when compared to women evaluated at both 28 and 32 weeks gestation (71.43% vs 33.33%, p<0.05).
Conclusions: Our results support the need for fetal ultrasound at 28 weeks gestation to direct metabolic therapy since insulin administration introduced after 32 weeks gestation has a poor effect on fetal growth.