Need some assistance
Assisted vaginal delivery may be necessary when maternal efforts cannot result in the delivery of a baby.
THE second stage of labour starts from the time the cervix is dilated to 10cm until the baby is born. Some women may require assistance from the attending healthcare professional (accoucheur), who is usually a doctor, to deliver the foetus.
Assisted vaginal delivery may be necessary when maternal efforts cannot result in delivery of the foetus. It is done when there is a prolonged second stage, which is generally defined as a lack of progress for two hours if there is no regional analgesia for pain relief, or three hours if there is regional analgesia in women having their first baby (nulliparous); or a lack of progress for one hour without regional analgesia, or two hours with regional analgesia in women having subsequent babies (multiparous).
Another reason for assisted vaginal delivery is a non-reassuring foetal heart rate or other indicators of immediate or potential foetal distress. Some women may need to have the second stage shortened for their benefit, eg cardiac disease, maternal exhaustion.
The incidence of assisted vaginal delivery varies. It is about 10 to 15% in developed countries.
Vacuum extractor and forceps
There are two instruments used in assisted vaginal delivery: vacuum extractor (ventouse) and forceps.
The ventouse is an instrument that uses suction to deliver the foetus. A soft or hard plastic or metal cup, connected by a tube to a suction device, is attached to the foetal head. The instrument is switched on and the suction pressure gradually increased.
This leads to the firm application of the suction cup to the foetal head. The motherto-be is encouraged to push during a contraction. At the same time, the accoucheur gently pulls on the ventouse to help deliver the foetus.
The forceps is a metal instrument that has two smooth blades with handles. It is shaped like a large spoon and is curved to fit the sides of the foetal head. Each blade of the forceps is carefully applied to the foetal head and joined together at the handles.
During a contraction, the mother-to-be is encouraged to push and the accoucheur gently pulls on the forceps to help deliver the foetus.
There are different types of forceps. Some are designed specially to rotate the foetal head, ie if the back of the foetal head is facing the mother-to-be’s side (transverse position), or it is facing the mother-to-be’s back (occipito-posterior position).
The type of forceps appropriate to the clinical situation will be chosen by the accoucheur.
The ability to perform an assisted vaginal delivery with the ventouse and/or forceps is a considered a critical aspect of basic emergency obstetric care by the World Health Organisation.
Prior to applying a ventouse or forceps, the accoucheur will carry out an assessment to determine whether the foetus can be safely delivered vaginally. This involves an abdominal and vaginal examination.
A ventouse or forceps will not be used if there is cephalo-pelvic disproportion, ie the maternal pelvis is not big enough for the foetal head or body; the foetal head is not engaged (the largest diameter of the foetal head has not entered into the smallest diameter of the maternal pelvis); the foetus is less than 34 weeks gestation; the foetus is presenting by the face, breech or shoulder; or if there are known foetal conditions affecting its bone or clotting.
If the accoucheur is unsure whether the foetus can be delivered vaginally, the assisted vaginal delivery will be carried out in an operating theatre so that there is early recourse to Caesarean section if attempts at assisted vaginal delivery fail.
Adequate pain relief is provided during an assisted vaginal delivery. It can be local or regional analgesia. The former involves injecting a local anaesthetic into the vagina (pudendal block) to numb both left and right pudendal nerves that supply the birth canal.
The latter involves inserting a plastic tube (catheter) into the space just outside the spinal cord (epidural), or into the spinal canal (spinal), to numb the nerves in the back that supply the birth canal.
It is usual for the bladder to be emptied for an assisted vaginal delivery. This involves inserting a catheter into the bladder.
Ventouse or forceps
The ventouse and forceps are both safe and effective if used by an experienced accoucheur. The choice of a ventouse or forceps depends on the accoucheur’s experience, and the clinical situation.
The Cochrane Database of Systematic Reviews in 2010, which included 32 studies (6,597 women) in their review ( http://summaries. reported:
“Forceps were less likely than the ventouse to fail to achieve a vaginal birth. However, with forceps, there was a trend to more Caesarean sections, and significantly more third- or fourth-degree tears (with or without episiotomy), vaginal trauma, use of general anaesthesia, and flatus incontinence or altered continence.
“Facial injury was more likely with forceps. There was a trend towards fewer cases of cephalohaematoma (which is a localised effusion of blood beneath the periosteum of the skull of the newborn, due to rupture of the vessels crossing the periosteum during birth) with forceps.
“Among the different types of ventouse, the metal cup was more likely to result in a successful vaginal birth than the soft cup, with more cases of scalp injury and cephalohaematoma.
“Overall, forceps or the metal cup appears to be most effective at achieving a vaginal birth, but with increased risk of maternal trauma with forceps and neonatal trauma with the metal cup.”
The rates of neonatal cephalohaematoma and retinal haemorrhage were higher in ventouse deliveries than forceps deliveries. These haemorrhages usually resolve without sequelae within four weeks of birth, but the cephalohaematoma can lead to jaundice (hyperbilirubinaemia).
One study showed no differences in vision problems or in child development five years after a ventouse or forceps delivery.
Assisted vaginal delivery is a risk factor for shoulder dystocia, an emergency situation in which the foetal shoulder in front cannot pass under the maternal pubic bone or requires manipulation by the accoucheur to do so, and it appears to be more common with the ventouse than with forceps delivery. The incidence of shoulder dystocia increases in cases of big foetuses, ie 4.5kg or more (macrosomia).
Bleeding within the skull (intracranial haemorrhage) and in the potential space between the skull and the scalp aponeurosis (subgaleal or subaponeurotic haemorrhage) of the newborn are rare, but serious, events reported with the ventouse.
A study from Hospital Universiti Kebangsaan Malaysia reported that the incidence of subaponeurotic haemorrhage was significantly higher in neonates delivered by ventouse than by other modes of delivery (41.4 per 1,000 live births in neonates delivered by ventouse compared to one per 1,000 livebirths in neonates delivered by other modes). The neonates who developed subaponeurotic haemorrhage without trial of ventouse had a history of either prolonged labour or difficult delivery.
If a ventouse is used and the suction cup comes off, or if delivery has not been successful after a few pulls, the accouchueur may then decide to deliver the foetus by forceps or Caesarean section.
The Cochrane Database of Systematic Reviews in 2010 stated succinctly: “The role of operator training with any choice of instrument must be emphasised. The increasing risks of failed delivery with the chosen instrument from forceps to metal cup to hand-held to soft cup vacuum, and trade-offs between risks of maternal and neonatal trauma identified in this review need to be considered when choosing an instrument.”
Forceps after failed vacuum
In the past, forceps have often been considered after an unsuccessful attempt at ventouse delivery. However, several studies reported an increase in neonatal intracranial injury when both ventouse and forceps are applied.
One study reported that when both the ventouse and forceps were used, the incidence of intracranial haemorrhage was one in 256, which is 3.4 times the incidence when only the ventouse was used.
Another study reported a higher incidence of intracranial haemorrhage, brachial or facial nerve injury, and need for the newborn to be put on a ventilator when the ventouse and forceps were used sequentially, as compared to spontaneous delivery.
The various professional organisations of obstetricians and gynaecologists worldwide advise against the use of ventouse and forceps or vice versa sequentially, except in situations where the facilities for Caesarean section are not readily available.
After the delivery
After the baby has been delivered, the accoucheur will check the mother for any traumatic tears to the cervix, vagina, vulva or anal sphincter. Anal sphincter tears, which can result in anal incontinence, are often not diagnosed. The paediatrician will examine the newborn for signs of trauma.
Most women feel bruised and sore in their birth canal after a normal or an assisted delivery. There may be pain from the stitches and swelling. Analgesics for pain relief will be helpful.
An assisted delivery in the first pregnancy does not mean that another one will be needed in the next pregnancy. The vast majority of women have a normal delivery in a subsequent pregnancy.
A few women may be traumatised by their experience of giving birth. If there are such concerns, it is prudent to discuss the matter with doctor.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.