Study: O2 supplementation not superior to RA in improving UA lactate

According to research presented at the 2018 Annual meeting of the Society for Maternal-Fetal Medicine, room air (RA) is not inferior to O₂ for improving umbilical artery (UA) lactate in patients with Category II fetal heart tracings (FHT) during active labor. According to the authors, approximately two-thirds of women in labor receive O₂ to reverse perceived fetal hypoxemia and to prevent acidosis.    

In a randomized controlled non-inferiority trial conducted from June 2016 to June 2017, the researchers looked at 114 singleton pregnancies ³ 37 weeks with Category II FHT that required intrauterine resuscitation in active labor (³ 6 cm). The participants were randomized to receive either RA or 10L/min O₂ by facemask until delivery. The primary outcome was UA lactate measured by umbilical cord gases collected at delivery. Secondary outcomes were other UA gas components, cesarean delivery for nonreassuring fetal status, and operative vaginal delivery. Noninferiority was declared if the mean difference in lactate between RA and O₂ was < 1.0 mmol/L and analysis was by intention-to-treat.  

Of the 114 patients included in the study, 99 with paired cord gases were included in the intention-to-treat analysis. There were 48 patients who received O₂ and 51 patients who received RA. The researchers found no difference in mean UA lactate between the randomized 0₂ and RA groups (mean [95% CI], O₂ = 3.4 [3.0,3.8] vs RA = 3.5 [3.1, 4.0], P = 0.69). For UA lactate, the mean difference was 0.1 mmol/L (95% CI -0.5, 0.7). The researchers found no differences in other UA gas components, vaginal delivery or nonreassuring fetal status between the groups.