Background and aims Near-infrared spectroscopy (NIRS) is a non-invasive method to measure changes in the concentration of oxygenated (ΔO2Hb) and deoxygenated haemoglobin (ΔHHb). Changes in total haemoglobin (ΔcHb = ΔO2Hb+ΔHHb) give information on changes in cerebral blood volume (CBV). Moreover cerebral tissue oxygenation index (cTOI = ΔO2Hb/ΔcHb*100%) is detected.

The aim was to evaluate changes of CBV during postnatal transition in term newborns.

Methods This observational study was conducted at the Medical University Graz. Included were term infants without need for respiratory support after caesarean section. NIRS measurements were carried out with ‘NIRO-200-NX’ (Hamamatsu; Japan) over 15 min.

Results 109 term infants (55 female) with mean gestational age of 39+0 weeks (±7 days) and birth weight of 3245 g (±441) were included.

CBV: Related to the baseline at 2 min of age (min), median (25th; 75th percentiles) ΔcHb was 0 micromoles (µM) (-5;4) at 3 min, -1 µM (-8;5) at 5 min, -7 µM (-17;0) at 10 min, and -13 µM (-26;1) at 15 min. ΔcHb, representing the behaviour of CBV, was slowly decreasing during transition period.

cTOI: Median (25th;75th percentiles) cTOI was 56% (50;65) at 2 min, 57% (51;64) at 3 min, 64% (58;72) at 5 min, 74% (69;79) at 10 min, and 72% (67;78) at 15 min. cTOI was slowly increasing from 2 min to 7 min, reaching a steady state after 8 min.

Conclusion In healthy newborns CBV was slowly decreasing over the whole study period. We hypothesise, that increasing left-to-right shunt via ductus arteriosus may account for decreasing CBV in this period. These findings add information for a better understanding of haemodynamic processes during transition.