Failed Instrumental Delivery

Failed instrumental delivery is failure to deliver the baby with vacuum or forceps within the allowed number of pulls or time, or when the instrument slips or detaches. Causes are a wrongly judged position, a head higher than thought, cephalopelvic disproportion, poor traction technique, weak maternal effort and poor case selection. It matters because repeated or sequential attempts cause fetal head injury and severe maternal trauma, and the baby then needs delivery by caesarean section, often with a deeply impacted head.

• Risk factors: occiput posterior or transverse position, station above +2, large baby, obesity, prolonged second stage, inexperienced operator, epidural with poor pushing.
• Attempts are made only in a place where caesarean section can start at once (an attempt in theatre with the surgical team ready).
• Each failed attempt raises the chance of fetal injury.

After a correctly applied instrument and traction with contractions, the head does not descend, the cup detaches or the blades slip. The fetal heart may show decelerations during traction, and the mother is exhausted.

• No descent with 3 pulls, or the cup detaching twice, or 20 minutes of vacuum application.
• Marked caput and moulding develop during attempts.
• Differential diagnosis: occiput posterior or transverse malposition, cephalopelvic disproportion, wrong station assessment, asynclitism, deflexed head, weak expulsive effort, shoulder dystocia after the head delivers.
• Complications: fetal scalp injury, subgaleal haemorrhage, intracranial haemorrhage, facial nerve palsy, skull fracture, neonatal asphyxia, third and fourth degree tears, cervical or vaginal tears, postpartum haemorrhage, deep head impaction at caesarean section, maternal infection.

The diagnosis is made in theatre, by the failure of descent and by a check of the application and the position.

• Reassess position, station and flexion by vaginal examination; confirm bladder is empty.
• Check cup or blade placement and traction direction; count pulls, detachments and minutes of application.
• Cardiotocography or fetal heart auscultation between pulls; maternal pulse, blood pressure and blood loss.
• Record each step with times in the notes.

The principle is to stop after the limit is reached, avoid sequential instruments unless an expert judges success is certain, and deliver by caesarean section.

• Supportive: stop traction; tell the mother and the paediatric team; empty the bladder; two cannulae with group and cross-match 2 units; senior obstetrician and anaesthetist present; knee support for the mother in lithotomy; for a deeply impacted head, an assistant pushes the head up from below through the vagina while the surgeon delivers.
• Pharmacological: cefazolin 2 g IV as a single dose before incision (3 g above 120 kg); oxytocin 10 IU IM after birth, then 20 IU in 1 litre Ringer's lactate at 125 mL per hour for 4 hours; tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours); diclofenac 50 mg oral 8-hourly for 3 days if no contraindication; newborn vitamin K 1 mg IM.
• Procedures: caesarean section for failed vacuum or forceps; for a deeply engaged head, push the head up from the vagina or use reverse breech extraction; no more than one change of instrument, and only by an expert for a clear remedial reason; examine the baby for scalp and facial injury.
• Special groups: HIV positive women continue tenofovir 300 mg, lamivudine 300 mg and dolutegravir 50 mg oral once daily; women with a previous caesarean section need the scar inspected.
• Red flags: abnormal fetal heart rate, no descent after 3 pulls, scalp swelling spreading beyond the cup site, bleeding above 500 mL, pallor or floppy baby.
• Follow-up: newborn examination for subgaleal swelling, haematoma and nerve palsy with head circumference and haemoglobin checks; bladder catheter for 24 hours; wound and perineal care; review at 1 week and 6 weeks; plan the next birth with the surgical findings.