Assisted Vaginal Birth (Instrumental Delivery)

Last updated 20.09.12

 

Index

 

Definition

-  Vaginal birth of cephalic infant from labour with assistance of forceps or vacuum extraction

 

Features

-  Aim for NVB next delivery

-  80% success rate unless 3rd or 4th degree perineal tear

-  Should aim to avoid sequential instruments as increased trauma to infant

-  When vertex is at spines biparietal diameter has usually passed pelvic inlet = engagement

-  Outlet

-  Fetal scalp visible wo parting labia

-  Head at or on perineum

-  Skull on pelvic floor

-  Sagital suture AP or ROA or LOA (not greater than 45o)

-  Low

-  Leading part of skull at or below +2cm & not on pelvic floor

-  Mid

-  Fetal head not >2cm (1/5) palpable abdominally

-  On VE leading part >+2cm but not above spines

-  Head must be engaged

-  Vaccum vs Forceps

-  Vacuum

-  More likely to fail

-  Increased cephalohaematoma, retinal haemorrhage & maternal concern for baby

-  Less maternal vaginal & perineal trauma

-  No change in LUSCS rate, APGARs or need for phototherapy (jaundice)

-  Forceps

-  More force required to deliver

-  Higher analgesia requirements

-  Faster delivery

-  Increased facial nerve injuries

-  Fetal Measurements

-  OA (Subocciptiobrematic) = 9.5cm

-  OP (Occipitofrontal) = 11cm

-  Brow (Supraoccipitomental) = 13.5cm

-  Face (Submentobregmatic) = 9.5cm

-  Transverse (Biparietal) = 9.5cm

-  Maternal Measurements

-  Inlet

-  AP (true conjugate) = 11.5cm

-  Transverse = 13.5cm

-  Midpelvis

-  AP = 12cm

-  Bispinous = 10.5cm

-  Outlet

-  AP = 11.5cm

-  Bituberous = 11cm

 

 

Prevention

-  Partogram

-  Upright or later position in labour

-  Avoidance of epidural

-  Use of oxytocic for primips with epidural

-  Delayed pushing in primips with epidural

-  Continuous support in labour

-  Consider manual rotation

-  Consider if LUSCS more appropriate

 

Indications

-  Requirement to expediate vaginal birth

-  Fetal indications

-  Non reassuring CTG or scalp lactate

-  2nd stage placental abruption or cord prolapse

-  Any condition which makes it unsafe for fetus to remain in uterus

-  Aftercoming head of breech (forceps)

-  At LUSCS (forceps)

-  Maternal indications

-  Need to avoid strong pushing: CCF, HTN, cerebrovascular disease, Myasthenia, spinal cord injury

-  Inadequate progress

-  Nuliparous 3hrs w epidural or 2hrs wo

-  Mulitparous 2hrs w epidural or 1hr wo

-  Maternal fatigue/exhaustion

 

Contraindications/Precautions

-  Relative: fetal bleeding diathesis (no vacuum, +/- forceps), HIV, HCV

-  Prior to full dilation

-  Unless prolapsed cord in multip at 9cm or second twin

-  Fetal osteogenesis imperfecta

-  Face presentation can only use forceps

-  Prematurity <34/40 can only use forceps

 

Procedure

-  Explanation & consent

-  Site

-  If predict failure or high risk perform in OT

-  BMI >30

-  Midcavity or 1/5+ palpable abdominally

-  EFW >4kg or clinically big baby

-  OP position

-  Abdominal exam ensure

-  Vertex presentation

-  1/5+ station

-  Uterus contracting adequately

-  VE ensure

-  Full dilation

-  Membranes ruptured

-  Vertex at or below ischial spines

-  Empty maternal bladder: IDC, in-out catheter

-  Analgesia: PO, +/- regional block (pudendal block)

-  Consider perineal infiltration with LA

-  R/V for ?mediolateral episiotomy

-  Abandon attempt if

-  No progression of descent w traction on each pull

-  Disengagement of cup x3 on vacuum

-  Birth not imminent after traction on x3 consecutive contractions of correctly fitted instrument

-  Failed vacuum

-  Attempt forceps delivery

-  Caesarean (LUSCS)

-  Failed forceps

-  Caesarean (LUSCS)

 

Post Delivery

-  Venous & arterial cord gases

-  Document

-  Repair of perineal trauma/episiotomy

-  Monitor urine output for 24hrs (to avoid retention)

-  Analgesia

-  Paracetamol + Diclofenac regular

-  +/- ice pack

-  Consider Enoxaparin for DVT prophylaxis

-  Inspect infant for signs of injury

 

Complications

-  Maternal

-  Perineal trauma

-  PPH

-  VTE: DVT

-  Neonatal

-  Cephalohaematoma

-  Intracranial haemorrhage

-  Retinal haemorrhage

-  Subgaleal hamorrhage

 

 

 

References

 

RWH CPG: Assisted Vaginal Birth, 10/08/2007