Proposed cut-off for fetal scalp blood lactate in intrapartum fetal
surveillance based on neonatal outcomes: a prospective observational
study
Abstract
Objective Determination of lactate in fetal scalp blood (FBS) during
labor has been studied since the 1970s. The internationally accepted
cut-off of >4.8mmol/L indicating fetal acidaemia is
exclusive for the point-of-care device (POC) LactateProTM, which is no
longer in production. The aim of this study was to present a new cut-off
for scalp lactate based on neonatal outcomes with the use of
StatstripLactate®/StatstripXpress® Lactate system, the only POC lactate
meter designed for hospital use. Design Observational Study Setting
January 2016 to March 2020 labouring women with an indication for FBS
were prospectively included from seven Swedish and one Australian
delivery unit. Population Inclusion criteria: singleton pregnancy,
vertex presentation, ≥35+0 gestational weeks. Method Based on the
optimal correlation between FBS lactate and cord pH/lactate, only cases
with ≤25 minutes from FBS to delivery were included in the final
calculations. Main outcome measures Metabolic acidosis in cord blood was
defined as pH <7.05 plus BDecf >10 mmol/L and/or
lactate >10 mmol/L. Results 3334 women were enrolled of
which 799 were delivered within 25 minutes. The areas under the ROC
curves (AUC) and corresponding optimal lactate cut-off values were as
follows; metabolic acidosis AUC 0.87(95% CI:0.77-0.97), cut-off
5.7mmol/L; pH <7.0 AUC 0.83(95% CI:0.68-0.97), cut-off
4.6mmol/L; pH <7.05 plus BD ≥12mmol/L AUC 0.97(95%
CI:0.92-1), cut-off 5.8mmol/L; Apgar score <7 at 5 minutes AUC
0.74(95% CI:0.63-0.86), cut-off 5.2mmol/L; and pH <7.10 plus
composite neonatal outcome AUC 0.76(95% CI:0.67-0.85), cut-off
4.8mmol/L. Conclusions Suggested intervention threshold for fetal
acidemia is scalp lactate of 5.2mmol/L using the
StatstripLactate®/StatstripXpress®.