[Value of fetal scalp lactate sampling during labour: a comparative study with scalp pH]

Abstract

Objective: To evaluate the validity and the feasibility of fetal scalp lactate sampling during labour in the assessment of non reassuring fetal status.

Patients and method: A prospective observational study was conducted on 129 fetal scalp blood samplings. Scalp lactate measurements were compared to scalp pH (gold standard procedure), neonatal cord blood gas (pH and lactates) and Apgar score. Pathological values taken were for scalp lactates>5 mmol/l, scalp pH<7.20, cord arterial pH<7.10, cord arterial lactates>6,35 mmol/l, and Apgar score<7 at one and five minutes. All measurements were performed using the Rapid Lab 860 device from Bayer.

Results: Scalp lactate correlated significantly with scalp pH (R=-0.54, P=0.001), with umbilical artery pH (R=-0.46, P=0,01), with umbilical artery lactate (P=0.49, P=0.01), but with neither Apgar score at one minute (R=-0.21, ns) nor at 5 minutes (R=-0.11, ns). Scalp lactate at a cut-off value of 5 mmol/l had the same predictive values than scalp pH at 7.20 to predict neonatal acidosis. Sampling failure with scalp lactate was inferior to 1 vs 18% for scalp pH.

Discussion and conclusion: The measurement of lactate in fetal blood scalp seems correlated to the fetal scalp pH. It may be an attractive alternative to pH analysis and a useful tool for monitoring fetal asphyxia, especially with the advent of handheld devices requiring small sample volumes.