Obs: L&D - instrumental delivery and perineal tears

Question 1

what are the indications for an instrumental delivery

Answer 1

clinical judgement of midwife/obstetrician

• failure to progress
• fetal distress
• maternal exhaustion
• control of the head in various fetal positions

REMEMBER - epidural associated with increased risk when epidural in place

Question 2

what are some risks to the mother of an instrumental delivery?

Answer 2

• Postpartum haemorrhage
• Episiotomy
• Perineal tears
• Injury to the anal sphincter
• Incontinence of the bladder or bowel
• Nerve injury (obturator or femoral nerve)

Question 3

what are the main and rarer risks to baby of an instrumental delivery?

Answer 3

• Cephalohaematoma with ventouse
• Facial nerve palsy with forceps

rare

• Subgaleal haemorrhage (most dangerous)
• Intracranial haemorrhage
• Skull fracture
• Spinal cord injury

Question 4

describe a ventouse delivery

Answer 4

suction cup on a cord

suction cup goes on babys head and traction applied to cord to pull baby out

can cause cephalohaematoma - blood between skull and periosteum

Question 5

describe a forceps delivery

Answer 5

2 pieces of curved metal that attach together which go either side of babys head and grip it in a away that allows the doctor/midwife to apply careful traction and pull the head out

can leave bruises on baby’s face and can lead to fat necrosis on babys face

Question 6

what nerve injuries to the mother can rarely be caused by instrumental delivery?

Answer 6

femoral and obturator nerve injuries

usually resolve within 6-8 weeks

Question 7

describe how a woman may get a femoral nerve injury from an instrumental delivery and what she may experience as a result

Answer 7

compressed against the inguinal canal during forceps delivery

causes weakness of knee extension, loss of patella reflex and numbness of anterior thigh and medial lower leg

Question 8

describe how a woman may get a obturator nerve injury from an instrumental delivery and what she may experience as a result

Answer 8

may be compressed by forceps or by fetal head in normal delivery

weakness of hip adduction and rotation, numbness of medial thigh

Question 9

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.

Question 10

when do perineal tears occur?

Answer 10

where the external vaginal opening is too narrow to accommodate the baby

Question 11

what are some scenarios when perineal tears are common?

Answer 11

• First births (nulliparity)
• Large babies (over 4kg)
• Shoulder dystocia
• Asian ethnicity
• Occipito-posterior position
• Instrumental deliveries

Question 12

how are perineal tears classified?

Answer 12

• First-degree – injury limited to the frenulum of the labia minora (where they meet posteriorly) and superficial skin
• Second-degree – including the perineal muscles, but not affecting the anal sphincter
• Third-degree – including the anal sphincter, but not affecting the rectal mucosa
• Fourth-degree – including the rectal mucosa

Question 13

how are 3rd degree tears sub-classified?

Answer 13

• 3A – less than 50% of the external anal sphincter affected
• 3B – more than 50% of the external anal sphincter affected
• 3C – external and internal anal sphincter affected

Question 14

how are perineal tears managed?

Answer 14

first degree usually don’t require any sutures

anything larger than 1st degree usually requires sutures

3rd or 4th usually require theatre

• Broad-spectrum antibiotics to reduce the risk of infection
• Laxatives to reduce the risk of constipation and wound dehiscence
• Physiotherapy to reduce the risk and severity of incontinence
• Followup to monitor for longstanding complications

Question 15

when are women who have had a perineal tear offered CS for subsequent pregnncies?

Answer 15

if they are symptomatic after 3rd or 4th degree tears

Question 16

what are some short term complications of perineal tears and their repair?

Answer 16

• Pain
• Infection
• Bleeding
• Wound dehiscence or wound breakdown

Question 17

what are some longer lasting effects of perineal tears and their repair?

Answer 17

• Urinary incontinence
• Anal incontinence and altered bowel habit (third and fourth-degree tears)
• Fistula between the vagina and bowel (rare)
• Sexual dysfunction and dyspareunia (painful sex)
• Psychological and mental health consequences

Question 18

what is an episiotomy?

Answer 18

• obstetrician or midwife cuts the perineum before the baby is delivered
• done in anticipation of needing additional room for delivery of the baby (e.g. before forceps delivery)
• performed under local anaesthetic
• A cut is made at around 45 degrees diagonally, from the opening of the vagina downwards and laterally, to avoid damaging the anal sphincter - mediolateral episiotomy
• cut is sutured after delivery.

Question 19

what is perineal massage?

Answer 19

method for reducing the risk of perineal tears

involves massaging the skin and tissues between the vagina and anus (perineum)

done in a structured way from 34 weeks onwards to stretch and prepare the tissues for delivery