25 EFFECT OF UTERINE CONTRACTIONS ON HUMAN FETAL CEREBRAL OXYGENATION AND HAEMOGLOBIN CONCENTRATION MEASURED BY NEAR INFRARED SPECTROSCOPY (NIRS)

Abstract

The purpose of this study was to measure by NIRS changes in cerebral oxyhacmoglobin [HbO2] and deoxyhaemoglobin [Hb] concentrations during labour. Two optical fibres were placed via the cervix 3cm apart on the scalp of 8 term infants. Uterine contractions were divided into those with and without fetal bean rate (FUR) decelerations (a fall in FHR of ≥ 15 beats.min−1 for ≥ 15 sees). In 6 fetuses contractions without decelerations (n=44) were associated with falls in both [HbO2] and [Hb], by 0.50 ± SD 0.27 μmol.100g−1 and 0.78 ± 0.60 μmol.100g−1 respectively. In 5 of these 6 fetuses FHR decelerations were seen (n=20) and were also accompanied by falls in [HbO2], of 0.87 ± 0.54 μmol.100g−1, but [Hb] rose by 1.10 ± 0.60 umol.100g−1 (p<0.01 vs contractions without decelerations, ANOVA). In the remaining 2 fetuses both [HbO2] and [Hb] rose during contractions (n=18), by 0.71 ± 0.43 umol.100g−1 and 1.22 ± 0.55 μmol.100g± respectively, no FUR decelerations were seen. We conclude that: (1) NIRS allows non-invasive monitoring of cerebral oxygenation and haemoglobin concentration during labour; (2) In most infants studied normal uterine contractions were associated with falls in cerebral [HbO2] and [Hb]; (3) ConiracLions wilh FHR decelerations were associated with desaturation of cerebral haemoglobin.