Veeser M et al. – The analysis could clearly demonstrate a decreased risk of fetal acidosis associated with phenylephrine use. In addition with the findings for base excess (BE), this suggests a favorable effect of phenylephrine on fetal outcome parameters. The mechanism of pH depression is not related to pCO2.

• Literature was identified by a systematic search.
• Hypotension, hypertension, and bradycardia of the mothers, fetal acidosis defined as a pH<7.20, and the continuous variables base excess (BE) and arterial pCO2 of the neonates were recorded.
• Meta-analysis using the random effects model was performed, and the weighted mean difference (WMD) or risk ratio (RR), and 95% confidence interval (95% CI) were calculated.

• The criteria for eligibility were fulfilled by 20 trials including 1069 patients.
• The RR of true fetal acidosis was 5.29 (95%CI 1.62-17.25, ) for ephedrine vs. phenylephrine (P=0.006).
• BE values after ephedrine use were significantly lower than after phenylephrine (WMD -1.17; 95% CI -2.01--0.33).
• Umbilical artery pCO2 did not differ.
• Mothers treated with ephedrine had a lower risk for bradycardia (RR 0.17; 95%CI 0.07-0.43; P=0.004).
• No differences between vasopressors were observed for hypotension and hypertension.