Doppler velocimetry and the assessment of fetal well-being in normal and diabetic pregnancies.

Doppler ultrasound has been proposed as a useful addition to antepartum testing in high-risk pregnancies. Increased placental resistance has been associated with underlying placental vascular disease, as well as abnormal fetoplacental blood flow. Since pregnancies complicated by diabetes are at risk for these complications, the application of Doppler ultrasonography for such pregnancies has been evaluated by several investigators.Multiple investigations have examined the relationship between maternal blood glucose levels and abnormal Doppler waveforms in women with diabetes. Of the nine published studies, four found a correlation between Doppler indices and glucose control, as measured by mean blood glucose levels and glycosylated hemoglobin levels, while five did not. However, this apparent discrepancy may be explained by the fact that the majority of women studied were in good or excellent control, as this is currently the accepted standard of care. In fact, the one study performed in primarily non-diabetic women demonstrated that increases in maternal plasma glucose concentrations of 30 mg/dl were followed by significant rises in the mean pulsatility index in both the umbilical and carotid arteries. More dramatic was the finding by most investigators that systolic/diastolic (S/D) ratios in third-trimester umbilical arteries were elevated in women with evidence of diabetic microvascular disease. Elevated third-trimester S/D ratios were associated with adverse maternal and perinatal outcomes in these women, specifically pre-eclampsia and intrauterine growth retardation. In conclusion, although elevated Doppler indices correlated with adverse outcomes in diabetic pregnancies, Doppler indices may be elevated in the otherwise uncomplicated diabetic patient with associated microvascular disease and with a normal outcome. Therefore, the Doppler ultrasound assessment of fetal well-being in diabetic pregnancies must be interpreted with caution.