Dizygotic twin rate has increased by about 50% over the past two decades due to the wide use of ovarian stimulation regimes in the treatment of subfertility. Diagnosis can be made by ultrasound in the first trimester and the chorionicity has to be assessed before 14 weeks. Continuous cardiotocograph (CTG) monitoring of both twins is mandatory. There is no ideal time interval between delivery of the first and second twin. Continuous electronic fetal monitoring of the second twin is mandatory, after the birth of the first twin. Cord prolapse is more common after the delivery of the first twin and should be anticipated. Vaginal delivery is always preferable to caesarean delivery in low-resource settings when the first twin is vertex. When the second twin is non-vertex internal podalic version and breech extraction should be the aim over emergency caesarean delivery, if there are no other contraindications for vaginal birth.

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.