Electronic fetal monitoring (EFM) primary screening test is a highly sensitive test detecting a disease with a low prevalence. The fetal heart rate (FHR) trace or cardiotocograph (CTG) has five recognisable features: uterine activity, baseline FHR, baseline variability, accelerations and decelerations. The National Institute for Health and Clinical Excellence guidelines on EFM recommend that a CTG or FHR trace is classified into one of three groups: normal, suspicious or pathological based on the presence of reassuring and non-reassuring features. Fetal blood sampling (FBS) is used to identify compromised fetuses that need immediate delivery from those that are fine. There is a need for a monitoring system with a high specificity and sensitivity for detecting fetal acidosis and allowing timely and appropriate intervention without putting the fetus at risk. Currently, systems being researched include fetal ECG analysis and fetal oxygen saturation monitoring.