The goal of our study was to assess the breathing patterns of the fetuses of the mothers with well-controlled diabetes utilizing color and spectral Doppler technique. Fetal breathing-related nasal fluid flow was studied over gestational ages 28-40 weeks in 33 pregnancies complicated by diabetes and 62 uncomplicated pregnancies. Glycemic control was determined by fingerstick glucose value at the time of testing and HgbA1C drawn every 6 weeks. Each ultrasound examination consisted of the combination of gray scale imaging with color-flow and spectral Doppler analysis. In each case, 10 breath cycles were averaged for each of the following parameters: inspiratory peak and duration, expiratory peak and duration, and respiratory rate. A comparison of the study and control groups for each of the parameters was achieved by an analysis of covariance (ANACOVA). With adjustment for gestational age, no differences between the two groups were measured for any of the five parameters studied. However, there was a positive correlation between expiratory peak and gestational age (r = +0.20, P < 0.042) and between expiratory duration and gestational age (r = +0.24, P < 0.011). Respiratory rate was negatively correlated with gestational age (r = -0.32, P < 0.0006) Since similar fetal breathing patterns are seen across gestation utilizing color flow and spectral Doppler technique in both pregnancies with and without diabetes, this new modality may prove useful in the assessment of fetal well-being in both groups.