Sex related difference in cardiac output during neonatal transition in term neonates

The immediate transition from foetus to neonate includes substantial changes especially concerning the cardiovascular system. As sex related differences have been shown in cardiovascular medicine, this topic warrants further investigation in neonatology. Aim: The aim of this present study was to measure cardiac output (CO) and cerebral oxygenation (cTOI) non-invasively in term neonates and to investigate potential sex related differences between female and male neonates after birth.

This is a mono-centric prospective observational study. For CO-measurements, the electrical velocimetry method was used. The pulse oximetry for arterial oxygen saturation and heart-rate measurements was placed on the right hand or wrist. cTOI was measured using a NIRO 200NX monitor. The near-infrared spectroscopy probe was positioned on the right side of forehead in each infant. Monitoring started at minute 1 and was continued until minute 15 after birth. At minutes 5, 10, and 15 after birth, CO was calculated as an average out of six 10-second periods.

99 term neonates were enrolled. In our study population, we could identify 54 female and 45 male neonates. Males had higher cardiac output compared to females throughout the observational period, with a significant difference in minute 15 after birth (217, 95% CI: 203-231 mL/kg/min versus 178, 95% CI: 163-192 mL/kg/min; P<0.001). cTOI, SpO₂, and HR did not differ between male and female neonates.

The present work is the first to investigate sex related differences concerning cardiac output in term neonates during postnatal transition, showing a significantly higher cardiac output in male neonates 15 minutes after birth.