Background: Maternal diabetes mellitus is associated with fetal structural abnormalities, altered cardiac development, and changes in fetal growth. Ultrasonography provides a non-invasive method for evaluating these findings and assessing fetal well-being. Aim: To evaluate fetal cardiac changes and other significant ultrasonographic findings in pregnancies complicated by diabetes mellitus and assess their association with the type of maternal diabetes and glycemic control. Methods: This descriptive observational cross-sectional study included 80 pregnant women with pregestational diabetes mellitus (PGDM) or gestational diabetes mellitus (GDM) attending a tertiary care centre in Maharashtra. Clinical and biochemical details, including maternal glycated haemoglobin (HbA1c), were recorded. Fetal ultrasonography was performed to assess structural anomalies, cardiac parameters, fetal growth, amniotic fluid, placental characteristics, and Doppler indices. Associations were evaluated using appropriate statistical tests, with p<0.05 considered statistically significant. Results: Fetal structural anomalies were detected in 10 (12.5%) pregnancies. Anomalies were observed in 6/26 (23.1%) women with PGDM and 4/54 (7.4%) with GDM, although this difference was not statistically significant (p=0.070). Interventricular septal (IVS) hypertrophy was significantly more frequent in PGDM than GDM (26.9% vs 5.6%; p=0.011), as was cardiomegaly (23.1% vs 1.9%; p=0.004). Mean IVS thickness was also greater in PGDM. Compared with controlled glycemia, uncontrolled glycemia was associated with higher frequencies of polyhydramnios (30.6% vs 9.1%; p=0.021), IVS hypertrophy (22.2% vs 4.5%; p=0.037), and cardiomegaly (16.7% vs 2.3%; p=0.042). Fetal estimated weight and abdominal circumference were also higher in the uncontrolled group. Conclusion: Fetal ultrasonography identified structural and cardiac abnormalities in pregnancies complicated by diabetes. Cardiac changes were more frequent in PGDM