Awareness about normal cardiac volumes in the neonatal period is very important for understanding the cardiac function; however, the small cardiac size of neonates makes it difficult to perform invasive examinations. Three-dimensional echocardiography is used to evaluate cardiac volumes in children. However, no studies using this method have examined left ventricular volumes in neonates during the early neonatal period.

The study group consisted of 255 normal neonates. Comparisons of the stroke volume calculated according to the velocity–time integral and Pombo method were made.

The volumes in both end-diastole and end-systole and the stroke volume gradually decreased over time after birth. Participants with continuous a persistent ductus arteriosus flow had higher stroke volumes than those without persistent ductus arteriosus. The average end-diastolic volume per body surface area (m2) was 30.61 ml/m2 in boys and 29.80 ml/m2 in girls, whereas the ventricular end-systolic volume was 12.89 ml/m2 in boys and 12.80 ml/m2 in girls among the participants without persistent ductus arteriosus. The average stroke volume was 17.70 ml/m2 in boys and 17.00 ml/m2 in girls. Statistically significant gender differences were observed in the end-diastolic volume (p = 0.0053), stroke volume (p < 0.0001), and ejection fraction (p = 0.039). The cardiac index was calculated to be 2.04 L/minute/m2 in boys and 1.95 L/minute/m2 in girls, which was significantly lower than that calculated using the velocity–time integral and Pombo method (p < 0.0001).

Significant gender differences in the end-diastolic volume, stroke volume, and ejection fraction at birth were revealed. The cardiac index in the early neonatal period was found to be relatively smaller than what had previously been recognised.