Published online by Cambridge University Press: 06 May 2021
Operative vaginal birth rate has been stable in the United Kingdom at about 10%–13% [3, 4]. The caesarean section at full dilation as an alternative approach to instrument delivery has a high maternal and neonatal morbidity, but failed instrument vaginal deliveries (FID), which lead to caesarean sections, are associated with potentially serious maternal and fetal complications such as angular tears, postpartum haemorrhage, difficulty in delivery of the fetal head, fetal ischaemic-hypoxic injuries, birth trauma and perinatal deaths. Therefore, it is important to identify factors which can help to predict successful operative vaginal delivery.
There are various established risk factors which increase the chances of instrument delivery, including advanced maternal age, high body mass index (BMI; >30), high birth weight (>4.0 kg) and epidural analgesia.