OBJECTIVE The purpose of this study was to establish normal values for fetal heart function in the first trimester. METHODS This was a prospective observational study with institutional ethics approval and written maternal consent. Thirty-two healthy pregnant women were recruited, and transabdominal fetal echocardiography was performed between 12 and 14 completed weeks' gestation. Myocardial function was assessed with the myocardial performance index to assess combined systolic and diastolic function, isovolumetric contraction time to assess systolic function, and isovolumetric relaxation time to assess diastolic function. Mitral and tricuspid inflows were also assessed by determining the ratio between passive and active ventricular filling. The ventricular outflows were also assessed by peak systolic velocities (PSVs) and time velocity integrals (TVIs). RESULTS The mean gestational age at the time of echocardiography was 13 weeks, and the mean crown-rump length was 79 mm. All fetuses had a normal nuchal translucency measurement (mean, 1.5 mm). The myocardial performance index was the same in the left and right sides of the heart, 0.5. The mean isovolumetric relaxation time and isovolumetric contraction time on the left side of the heart were 41 and 36 milliseconds, respectively. The mean passive/active ventricular filling ratio was 0.6 at both the mitral and tricuspid valves. The mean aortic PSV was 26 cm/s, and mean pulmonary artery PSV was 32 cm/s. The mean aortic outflow TVI was 3.6 cm, and the mean pulmonary outflow TVI was 4.1 cm. CONCLUSIONS This study establishes normal values for cardiac function at 12 to 14 weeks' gestation. These values may assist in assessment of fetal health in early pregnancy.