Instrumental delivery refers to a vagina delivery assisted by either a ventouse suction cup or forceps. Tools are used to help deliver the baby’s head. About 10% of births in the UK are assisted by an instrumental delivery.
The procedure can usually be carried out on the labour ward. However, if there are concerns about whether it will be successful, the woman may be moved to theatre so that rapid delivery by caesarean section can be performed if necessary.
A single dose of co-amoxiclav is recommended after instrumental delivery to reduce the risk of maternal infection.
Indications
The decision to perform an instrumental delivery is based on the clinical judgement of the midwife or obstetrician. Some key indications are:
- Failure to progress
- Fetal distress
- Maternal exhaustion
- Control of the head in various fetal positions
TOM TIP: It is worth remembering there is an increased risk of requiring an instrumental delivery when an epidural is in place for analgesia.
Risks
Having an instrumental delivery increases the risk to the mother of:
- Postpartum haemorrhage
- Episiotomy
- Perineal tears
- Injury to the anal sphincter
- Incontinence of the bladder or bowel
- Nerve injury (obturator or femoral nerve)
The key risks to remember to the baby are:
- Cephalohaematoma with ventouse
- Facial nerve palsy with forceps
Rarely there can be serious risks to the baby:
- Subgaleal haemorrhage (most dangerous)
- Intracranial haemorrhage
- Skull fracture
- Spinal cord injury
Ventouse
A ventouse is essentially a suction cup on a cord. The suction cup goes on the baby’s head, and the doctor or midwife applies careful traction to the cord to help pull the baby out of the vagina.
The main complication for the baby is cephalohaematoma. This involves a collection of blood between the skull and the periosteum.
Forceps
Forceps look like large metal salad tongs. They come as two pieces of curved metal that attach together, go either side of the baby’s head and grip the head in a way that allows the doctor or midwife to apply careful traction and pull the head from the vagina.
The main complication for the baby is facial nerve palsy, with facial paralysis on one side.
Forceps delivery can leave bruises on the baby’s face. Rarely the baby can develop fat necrosis, leading to hardened lumps of fat on their cheeks. Fat necrosis resolves spontaneously over time.
Nerve Injuries
Rarely an instrumental delivery may result in nerve injury for the mother. This usually resolves over 6 – 8 weeks. The affected nerves may be:
- Femoral nerve
- Obturator nerve
The femoral nerve may be compressed against the inguinal canal during a forceps delivery. Injury to this nerve causes weakness of knee extension, loss of the patella reflex and numbness of the anterior thigh and medial lower leg.
The obturator nerve may be compressed by forceps during instrumental delivery or by the fetal head during normal delivery. Injury causes weakness of hip adduction and rotation, and numbness of the medial thigh.
Three other nerve injuries can occur during birth that are usually unrelated to instrumental delivery:
- Lateral cutaneous nerve of the thigh
- Lumbosacral plexus
- Common peroneal nerve
The lateral cutaneous nerve of the thigh runs under the inguinal ligament. Prolonged flexion at the hip while in the lithotomy position can result in injury, causing numbness of the anterolateral thigh.
The lumbosacral plexus may be compressed by the fetal head during the second stage of labour. Injury to this network of nerves nerve can cause foot drop and numbness of the anterolateral thigh, lower leg and foot.
The common peroneal nerve may be compressed on the head of the fibula whilst in the lithotomy position. Injury to this nerve causes foot drop and numbness in the lateral lower leg.
Last updated September 2020