Hyperglycemia during organogenesis is associated with an increased risk of congenital cardiac defects (CHDs). The pathophysiology leading to CHDs is not completely uncovered. However, elevated oxidative stress is considered to be the primary trigger that causes CHDs in fetuses of diabetic mothers. Maternal diabetes has been found to increase the risk for all types of CHDs. Diabetes may also impact the fetal cardiac performance at all gestational ages. Early detection of CHDs has certain advantages, such as making early decision about termination of pregnancy, enabling early genetic testing, and early reassurance if scan is normal. Combined transabdominal and transvaginal approach at 13–14 weeks of gestation is a reasonable strategy to assess fetal heart in diabetic women. Diagnostic accuracy of early fetal echocardiography has reached to above a reasonable cutoff when it is done in the late first trimester or early second trimester in the hands of expert sonographers. However, the literature is less certain to provide a firm conclusion about functional heart assessment in fetuses of diabetic mothers.