Abstract: BACKGROUND: The intrauterine environment is a key determinant for long-term health outcomes. Adverse fetal environments, such as maternal diabetes, obesity and placental insufficiency are strongly associated with long-term health risks in children. Little is known about differences in fetal cardiac output hemodynamics of diabetic mothers (DM) vs. non-diabetic mothers (NDM). Our study aims to investigate the left-sided, right-sided, and combined cardiac output (CCO) in fetuses of DM vs. NDM. METHODS: Retrospective data were collected in fetuses of DM (N = 532) and NDM (103) at mean gestational age 24 weeks. Examination included 2D echo and pulse wave Doppler. Wilcoxon rank sum tests and Chi-square tests were used to test for distribution difference of maternal and fetal continuous and categorical measures respectively between DM and NDM. Intraclass correlation coefficients were calculated to assess intra-observer reliability of fetal cardiac measurements. RESULTS: DM mothers had higher mean weight (89.7±22.2 kg) than NDM (76.8±19.8 kg), p < 0.0001 and higher mean BMI (33.4±7.5) than NDM (28.3±5.8), p < 0.0001. C-section delivery occurred in 66% of DM vs. 35% of NDM fetuses. Fetuses of DM mothers had significantly larger semilunar valve diameter, higher left ventricular (LV) output, higher combined cardiac output and lower right ventricle /left ventricle ratio compared to NDM. CONCLUSION: The greater CCO (adjusted for fetal weight), left sided cardiac output in the fetuses of DM, compared to NDM, represent differences in cardiac adaptation to the diabetic environment.