Abstract
Objective Determination of lactate in fetal scalp blood (FBS)
during labour 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
acidaemia is scalp lactate of 5.2mmol/L using the
StatstripLactate®/StatstripXpress®.
Keywords Fetal scalp blood, Lactate, Metabolic acidosis,
Umbilical cord blood, Fetal monitoring, Intrapartal asphyxia,
Cardiotocography and Point of Care