What the standard says
When intervention is indicated in a vaginal birth, the choice of intervention is based on the clinical situation, the benefits and risks of each option and discussion with the woman.
What this means for clinicians
When an instrumental vaginal birth is indicated and more than one instrument may be appropriate, the choice of intervention should take into account evidence of the relative benefits and risks of the various instruments, the clinician’s skill and the woman’s preference.
Instrumental vaginal birth may be indicated when there is:
- Fetal compromise
- A need to reduce the effects of the second stage of labour because of a medical condition
- Slow progress in the second stage of labour, associated with risks to the woman or fetus.
Current guidance from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists and the Royal College of Obstetricians and Gynaecologists (RCOG) include recommendations regarding the conditions for a safe instrumental vaginal birth (see Box 3).
Box 3: Conditions required for safe instrumental vaginal birth
Safe instrumental vaginal birth requires a careful assessment of the clinical situation, clear communication with the woman, and should be performed by, or in the presence of, an operator with expertise in the chosen procedure and the management of any complications which may arise.
For further detail see Royal Australian and New Zealand College of Obstetricians and Gynaecologists. 6. Instrumental vaginal birth. Melbourne: RANZCOG; 2016.
Clinicians should discuss with the woman the evidence regarding the risk profiles for both forceps and vacuum-assisted birth, as well as the benefits and risks of an unplanned caesarean section.
Forceps use is associated with increased risk of a third or fourth degree perineal tear and other vaginal trauma compared with vacuum-assisted birth. Both carry a small risk of any neonatal injury, but the nature of injuries differs between instruments (see Table 2).
Table 2: Summary of risk associated with forceps and vacuum-assisted birth
Forceps compared with vacuum
|
Risk estimate
|
Absolute rates
(% of operative births)
|
More likely to cause
|
|
|
- Third or fourth degree tears
|
RR; 1.89 (95% CI 1.51–2.37)
|
14% vs 7%
|
- Any type of vaginal trauma
|
RR; 2.48 (95% CI 1.59–3.87) |
26% vs 12%
|
|
RR; 5.10 (95% 1.12–23.25) |
1.7% vs 0.2%
|
More likely to
|
|
|
|
RR; 0.65 (95% CI 0.45–0.94)
|
91% vs 86% successful vaginal birth
|
No significant difference between instruments
- Any neonatal injury
- Low Apgar score (<7) at 5 minutes
- Low pH (<7.2) in umbilical artery at birth
|
|
|
CI = confidence interval; RR = relative risk
During a first vaginal birth where instruments are used, medio-lateral episiotomy (with an incision angle of 60°) reduces the risk of a third or fourth degree tear. Tools to help ensure the correct angle of incision include special episiotomy scissors, such as Episcissors‑60, which may assist midwives and obstetricians achieve a post-suturing angle of 40–60°. The protective effect of episiotomy is highest when forceps are used, especially with a first time vaginal birth.
Additional planning is recommended in case a vaginal birth is not achieved with the first approach, and the risks of subsequent options should be considered (for example, sequential use of instruments or caesarean section at full dilation).
Early discussion during pregnancy about these possible interventions may help prepare the woman should she face this situation. The discussion and her consent should be documented in her healthcare record.