Page created on November 24, 2021. Last updated on January 14, 2022 at 10:28
Definition and epidemiology
Operative delivery (or assisted vaginal delivery) refers to using special tools to assist vaginal birth, either forceps or vacuum extraction. It’s only performed during the second stage of labour. These tools allow the operator to apply both pulling forces and, in case of forceps extraction, rotation forces as well.
Like C-section, operative delivery carries some risk to the mother and foetus and so is only used when the risk of not performing it outweighs the risk of performing it.
There may be many indications for operative delivery. These are some of the more common:
- Foetal malposition
- Prolonged second stage of labour
- Foetal distress/asphyxia
- Maternal disease or complications
The two options for operative delivery are vacuum extraction and forceps extraction.
Vacuum extraction involves applying cup with suction to the foetal head and gently pulling when the mother is contracting. Pulling must be firm but gentle. Rotation cannot be applied to vacuum extraction. Vacuum can, unlike forceps, also be used for foetuses who have suffered intrauterine death.
Forceps extraction involves using a special forceps which “grabs” the foetus and gently pulling when the mother is contracting. Different forceps exist for different foetal head positions and presenting parts. Rotation can be applied to forceps extraction.
An episiotomy may be made routinely before attempting operative delivery to reduce the risk of anal sphincter injury.
When considering operative delivery, it’s important to know the foetal station, as a lower station is associated with a lower risk of complications. The station is defined as the distance (in centimetres) between the presenting part and the ischial spine, ranging from -5 to +5.
- -5 to -1 – Head is 5 – 1 cm above the ischial spine (not yet engaged)
- 0 – Head is at the level of the ischial spine
- +1 to +3 – Head is 1 – 3 cm below the level of the ischial spine
- +4 – Head is at the level of the pelvic floor
- +5 – Head is 1 cm below the level of the pelvic floor
Knowing the station is important as it will decide whether operative delivery is possible at all and, if it is, which equipment can be used. We classify operative delivery as the following:
- High – Station -1 to -5 (head is not engaged)
- Mid – Station +1 to 0
- Low – Station +3 to +2
- Outlet – Station +4 to +5
High operative delivery is never performed (C-section instead), and mid operative delivery is generally avoided.
As already mentioned, different forceps exist for different purposes. It’s important to choose a forceps appropriate for the size and shape of the fetal head and maternal pelvis, which should match the size, cephalic curve, and pelvic curve of the forceps. The foetal head position, rotation, and station are also important.
A forceps consists of a blade, shank, handle, and lock. The blade has both a cephalic curve (curves around the foetal head) and a pelvic curve (curves with the maternal pelvis).
The most frequently used forceps are:
- Simpson forceps
- Elliot forceps
- Naegele forceps
- Shute forceps – used for preterm delivery
- Kielland forceps – used to apply rotation
In order to perform operative delivery, several prerequisites must be fulfilled:
- The operator must have had practice
- The cervix must be fully dilated
- The membranes must have ruptured
- The foetal head must have passed the pelvic inlet (be engaged)
- There must be no cephalopelvic disproportion
Unlike C-section, operative delivery has several contraindications:
- Cervix not fully dilated
- Foetal position not reliably known
- Foetal head is not engaged
- Foetal malpresentation
- Cephalopelvic disproportion
- Preterm labour
Operative delivery carries the risk for complications to both the mother and foetus:
- Soft tissue injury
- Injury to vagina, bladder, rectum, nerves
- Facial paresis
- Skull fracture
- Intracranial haemorrhage
Cephalhaematoma is a complication unique to vacuum delivery. It’s a haematoma between the skull and periosteum. It’s a self-limiting complication which heals after weeks/months.