Maternal oxygen exposure may not change umbilical cord venous partial pressure of oxygen: non-random, paired venous and arterial samples from a randomised controlled trial
Yunhai Chuai, Wen Jiang, Xiaobin Xu, Aiming Wang, Yuanqing Yao, Lei Chen
Abstract
Abstract Background Despite the widespread use of oxygen (O 2 ) in intrauterine resuscitation, the obstetric scientists’ understanding of O 2 therapy is full of contradictions. We tested the hypothesis that higher maternal arterial partial pressure of oxygen (PO 2 ) is associated with higher umbilical cord venous PO 2 (UvPO 2 ). Methods This is a planned secondary analysis of a randomised controlled trial (RCT), 443 normal women were 1:1 randomly allocated to receive 2 L/min O 2 or room air from the onset of second stage to delivery. We reported that maternal 2 L/min O 2 exposure cannot affect the umbilical cord arterial pH or the fetal heart rate (FHR) pattern. In 217 non-random samples, we found 2 L/min O 2 exposure increased the maternal arterial PO 2 to the median 150 mmHg (hemoglobin would be saturated). The primary outcome for this analysis was UvPO 2 in these non-random samples. Results There were no significant differences between the O 2 group ( N = 107) and the control group ( N = 110) in the UvPO 2 (median 30.2, interquartile 25.4–35.2 versus median 28.3, interquartile 23.4–35.3, mmHg, P = 0.379). There were also no significant differences between room air and different percentiles of O 2 exposure duration (< 25th, ≧ 25th < 50th, ≧ 50th < 75th, ≧ 75th percentile) in the UvPO 2 . Conclusions Maternal O 2 exposure at super-physiological levels (median arterial blood PO 2 150 mmHg) in normal labor may not change the UvPO 2 . Clinical trial registration ClinicalTrials.gov NCT02221440 , first posted in 20 August 2014.