Assisted Vaginal Birth
RCOG Assisted Vaginal Birth (Green-top Guideline No. 26). Last reviewed: Apr 2020.
Definition
Assisted vaginal birth refers to the use of an instrument to facilitate vaginal delivery when spontaneous vaginal birth is not possible or safe.
Types and Classification
Instrument Types
Overview:
| Instrument | Description |
|---|---|
| Forceps | A metal instrument is applied to the sides of the fetal head to provide traction and/or rotation Subdivided into:
|
| Ventouse (vacuum extraction) | A suction cup is applied to the fetal scalp, creating a vacuum to assist traction with maternal pushing Available as soft cup or rigid cup devices |
Classification by Station and Rotation
| Classification | Station | Rotation required |
|---|---|---|
| Outlet | Scalp visible, skull at perineum | ≤45° |
| Low | +2 cm, not yet at perineum | Non-rotational (≤45°) / rotational (>45°) |
| Mid | ≤1/5 palpable abdominally, station 0/+1 cm | Non-rotational / rotational |
Decision to Perform Assisted Vaginal Birth
Before performing an assisted vaginal birth, three questions must be answered
- Clinical indication present?
- ALL clinical requirements met?
- Forceps or ventouse?
1. Clinical Indications
| Indication | Additional notes |
|---|---|
| Fetal compromise | This includes:
|
| Lack of progress in 2nd stage labour* | Lack of progress in nulliparous women:
Lack of progress in multiparous women:
|
| Maternal exhaustion or distress | The decision to intervene requires clinical judgment based on the maternal and fetal findings, the preferences of the woman, and the experience of the obstetrician |
| Medical indications to avoid the Valsalva manoeuvre (pushing) | Specific medical indications include:
|
*Lack of progress in 1st stage of labour is NOT an indication for assisted vaginal birth as it does NOT meet the requirement of ‘the cervix must be fully dilated’. In fact, assisted vaginal birth is strictly contraindicated before full cervical dilation.
2. Clinical Requirements
All 5 of the following requirements must be satisfied before proceeding with assisted vaginal birth:
| Requirement | Description |
|---|---|
| Fully dilated cervix (10 cm) + ruptured membranes |
Assisted vaginal birth is strictly contraindicated before full dilatation of the cervix |
| Fetal head engagement* | The fetal head must be ≤1/5 palpable per abdomen (in most cases, not palpable at all), and at the level of the ischial spines or below on vaginal examination |
| Fetal head position | The exact position of the fetal head must have been determined |
| Caput and moulding must be no more than moderate | Severe moulding indicates cephalopelvic disproportion and is a warning sign |
| Adequate maternal pelvis | The maternal pelvis must be deemed clinically adequate |
*Disclaimer: RCOG GTG 26 lists six requirements; fetal head engagement is presented here as a single criterion combining two separate guideline points (abdominal and vaginal assessment of head position) for clarity.
3. Choosing Forceps vs Ventouse
Assuming assisted vaginal birth is indicated AND meets the requirements
| Scenario | Recommendation |
|---|---|
| Prioritising maternal vs neonatal outcomes (general) |
|
| Preterm gestation | Forceps preferred over ventouse (due to premature infants’ susceptibility to cephalohaematoma, intracranial haemorrhage, subgaleal haemorrhage, and neonatal jaundice)
Exact recommendations:
|
| Suspected fetal bleeding disorders | Forceps preferred
|
| Malpresentation |
|
| Malposition (rotational births) | Acceptable options include:
|
Complications
| Complications more likely with forceps | Maternal:
Neonatal:
|
| Complications more likely with ventouse | General:
Various neonatal bleeding complications:
|
Unsuccessful Assisted Vaginal Birth
Definition
Definition of unsuccessful assisted vaginal birth (ANY of the following):
| Criterion | Instrument |
|---|---|
| Birth not imminent after 3 pulls (maximum number of pulls) | Both |
| Lack of progressive descent | |
| Poor application (forceps cannot be applied easily or the handles do not approximate easily) | Forceps |
| Failed rotation (during a rotational forceps birth, the baby’s head cannot be easily rotated with gentle pressure) | |
| Multiple detachments (the vacuum cap detaches 2 times) | Ventouse |
Subsequent Action
Generally, a Caesarean section is the necessary next step
If the initial attempt was made with forceps and it failed, do NOT attempt ventouse afterwards.
If the inital attempt was made with ventouse and it failed, consider low-cavity forceps judiciously (the operator must carefully weigh this decision).