Identifying fetuses with metabolic acidosis

A change in low-to-high frequency (LF/HF) ratio of fetal heart rate (FHR) variability greater than 30% in relation to a significant rise in the ST waveform on the fetal electrocardiogram (ECG) predicts cord artery metabolic acidosis (pH ≤7.05 and base deficit value >12.0 mmol/L) in infants, according to a case–control study from Scandinavia. The test yielded a sensitivity of 89% (95% CI, 68%–100%) and a specificity of 80% (95% CI, 64%–96%).

The researchers included 34 fetuses and measured the LF/HF ratio of FHR variability within 1 hour before and 1 hour after a significant ST event in the fetal ECG.

The authors of the study believe their findings should assist clinicians in separating hypoxic ST events from physiologic arousal reactions, thereby helping to reduce the number of unnecessary cesarean deliveries performed.