Fetal scalp sampling in labour

In the linked randomised controlled trial, Wiberg-Itzel and colleagues compare the effectiveness of two methods of diagnosing hypoxia in the fetus during labour—scalp pH analysis and scalp lactate analysis.1

Fetal wellbeing during labour depends on several factors—an adequate supply of oxygenated maternal blood reaching the placental intervillous space, gas exchange across an undamaged placenta, supply of oxygenated blood to the fetus through an open umbilical vein, and sufficient metabolic reserve in the fetus to withstand the hypoxic effects of uterine contractions. The fetus may be compromised by maternal hypotension, prolonged uterine contractions, placental abruption, umbilical cord occlusion, and fetal growth restriction. Distress may also occur for no obvious reason in apparently normal labours.

The traditional mainstay of fetal assessment during labour is monitoring of the fetal heart rate—either by intermittent auscultation (using a Pinard stethoscope or hand held Doppler device) or by continuous electronic monitoring. Compared with intermittent auscultation, continuous electronic monitoring has the disadvantage that it restricts the woman’s movement. It also increases …