Assisted vaginal birth refers to the use of a specially designed instrument to help with delivery during the last part of labor. It is also referred to as operative vaginal delivery, and accounts for about 5 percent of all deliveries in the USA.
Either forceps or vacuum extraction is used for delivery of the baby; however, over the last two decades forceps use has given way to vacuum extraction as the method of choice.
Indications for Assisted Birth
Early indications for assisted vaginal birth included danger to the life of the mother due to obstructed or prolonged labor rather than saving the life of the baby. For this reason, maternal safety was given top priority – even when there was the potential for fetal harm.
Today’s techniques are much safer, thus fetal wellbeing has now become the major reason for an operative vaginal delivery. This is often based on a nonreassuring fetal heart rate record, which is among the most popular indications today.
Other indications include:
- Prolonged second stage
- To shorten the second stage of labor
- Maternal exhaustion
There are several measures which may be adopted instead of operative vaginal delivery if the fetal heart rate is reassuring. For instance, if labor is prolonged but fetal parameters are within normal limits, oxytocin augmentation, giving the laboring patient more time, changes in maternal posture, reducing the level of epidural anesthesia, providing support to the patient working towards a normal delivery, and delayed pushing may all have a role to play in avoiding unnecessary assisted birth.
The advantages of such an approach include the freedom to resort to operative vaginal or cesarean delivery if these measures fail. It is important, therefore, to check the indication for operative vaginal delivery and the case-by-case situation before making a decision.
Certain conditions exist in which assisted vaginal birth is not a safe option for the fetus and should not, therefore, be considered. These include fetal disease – most notably bleeding diathesis or demineralization of bones, which could lead to intraventricular hemorrhage and fractures of the cranium, respectively, as well as the arrest or obstruction of labor, as shown by failure of fetal descent or cephalopelvic disproportion
Criteria for Assisted Birth
Some specific criteria have been set forth for an operative vaginal delivery to be considered. These include:
- Full dilatation of the cervix
- Rupture of membranes
- Engagement of the fetal head
- Documentation of fetal lie, presentation and position
Type of assisted birth is classified by the station of the fetal head and the degree to which it is rotated within the pelvis.
Contrasting Vacuum Extraction and Forceps
The vacuum device first developed by Malmstrom consisted of a stainless steel cup attached to a metal chain used for traction on the device once it was fixed on the fetal head. Nowadays disposable cups are used, of various materials such as plastic, polyethylene or silicone. These may be soft or rigid; the soft cup is funnel or bell-shaped, while the rigid one is mushroom-shaped.
Forceps were the earlier instruments used to extract fetuses from the birth canal. They are of several different sizes, but all of them end in a smooth curved metal blade with a large perforation in the center. This means they look like large spoons.
Forceps are designed to fit securely around the fetal head when applied correctly, and to be locked in position before traction is applied to pull the baby out gently. Some are even more helpful when the baby is stuck in the wrong position (such as occiput posterior) or in the vaginal outlet. They are more effective than the vacuum extractor in facilitating the birth, but are associated with slightly higher risks of maternal and fetal injury.
Failures and Complications
There are various reasons for the failure of vacuum or forceps extraction. They may include cephalopelvic disproportion, or wrong technique such as using the wrong size of cup in a vacuum extraction, including maternal tissue within the cup, or incorrect positioning of the cup or forceps on the fetal head.
From the maternal aspect, assisted vaginal delivery may increase the risk of:
- short-term and long-term damage to vaginal, perineal and anal tissues
- post-delivery perineal pain
- blood loss
- urinary retention which is usually transient
- incontinence of feces and/or urine
Potential fetal morbidities include:
- fetal scalp lacerations
- subgaleal hematomas
- intracranial hemorrhage
- facial nerve palsies