Identifying major and minor risk factors associated with failed induction of labour (IOL): A systematic literature review

Induction of labour (IOL) is a common obstetric intervention. Obstetricians’ decisions to proceed with IOL are influenced by various risk factors associated with induction failure, which can be classified as either major or minor. Following the PRISMA guidelines and using relevant keywords, a systematic literature search was conducted across four databases-PubMed, Embase, Cochrane Library, and Scopus-for empirical studies published between 2013 and 2024. Seventeen studies were deemed suitable for inclusion.From the selected papers, 21 statistically significant risk factors (P<0.05) associated with failed IOL were identified. A p-value threshold of 0.01 was used to differentiate between major and minor risk factors: factors with P<0.01 were categorised as major, while those with p ≥ 0.01 were considered minor.Identifying these risk factors is crucial for predicting which women are at a higher risk of failed induction and, therefore, more likely to experience complications or require emergency caesarean sections. Major risk factors identified include: pre-delivery BMI ≥ 25, gestational diabetes, cervical length > 25 mm, cervical shortening < 7 mm, initial cervical dilatation < 3 cm, maternal age > 30 years, Bishop Score ≤ 6, gestational age < 37 or > 42 weeks, occiput posterior position, birth weight ≥ 4 kg, nulliparity, premature rupture of membranes, absence of artificial membrane rupture with oxytocin, no previous vaginal delivery, maternal height < 163 cm, elevated foetal middle cerebral artery pulsatility index, and rural residence. Minor risk factors include the use of analgesia/anaesthesia, hypertensive disorders, lack of foetal engagement, and maternal indications for induction.While other factors may contribute to failed IOL, this study focused on those with statistical significance. The identification of major and minor risk factors lays the groundwork for future research aimed at stratifying patients by risk and potentially offering elective caesarean sections to those at high risk, thereby avoiding the dual risks of failed IOL and emergency surgery.