Adequate timing of fetal ultrasound to guide metabolic therapy in mild gestational diabetes mellitus - Results from a randomized study

Background. Ultrasound assessment of abdominal circumference early in the t hird trimester had been proposed to introduce insulin therapy in order to p revent fetal overgrowth in women with mild gestational diabetes mellitus. T he 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 tria l. Seventy-three women were evaluated at both 28 and 32 weeks gestation whe reas 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 exa ct test. Results. Twenty-nine women whose fetal abdominal circumference exceeded the 75th percentile were considered eligible for insulin therapy. In this grou p, we observed a statistically significant increase in the percentage of ma crosomic infants born from women whose ultrasound abdominal circumference a ssessment was performed only at 32 weeks gestation when compared to women e valuated 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 introduc ed after 32 weeks gestation has a poor effect on fetal growth.