BACKGROUND Approximately 30% of babies born in India are low birth weight (LBW) and about 70% of LBW babies are small for gestational age (SGA). Though there are several trials that have evaluated cardiac function of intrauterine growth restricted (IUGR) babies in utero, there is limited data about postnatal cardiac function in SGA babies during early neonatal period. This study was conducted to evaluate the cardiac functions of SGA babies by serial echocardiographic measurements and compare this with appropriate for gestational age (AGA) babies during the early postnatal period. METHODS Seventy babies were enrolled in this prospective observational study with 35 each in the SGA and AGA groups. Echocardiography was performed for all babies on days 1, 2, and 3 of life. Myocardial performance index (MPI) was used as the primary measure to compare cardiac function. MPI was calculated for both ventricles using pulse wave Doppler and tissue Doppler. RESULTS MPI of the left ventricle was significantly higher in the SGA group as compared to AGA babies during all the three measurement periods with SGA babies having significantly higher MPI of right ventricle on day 1 and day 2 but not on day 3. Left ventricular internal diameter index during diastole and systole (LVIDD index and LVIDS index), left atrium: aortic root ratio (LA:AO ratio) were significantly increased in SGA babies on all the occasions. Fractional shortening, ejection fraction, and area shortening were similar in two groups. CONCLUSIONS Myocardial performance index of left and right ventricle, which evaluates both systolic and diastolic function of ventricles, was significantly increased in SGA babies in comparison to AGA babies during the first 3 days of life except MPI of the right ventricle on day 3. Thus, SGA babies have compromised cardiac function through all phases of the cardiac cycle with the performance improving spontaneously over time.