Vacuum Assisted Delivery Training
Vacuum Delivery for Mothers and Others
This section has a two-fold purpose: firstly it has been designed for the information of mothers and other interested persons and, secondly, for use as a summary of vacuum extraction for health care providers who assist women in childbirth or care for infants in the neonatal period after vacuum delivery. This chapter is adapted from the Choices with Childbirth - Vacuum assisted delivery CD-ROM. Click here to see more Vacuum-assisted Delivery training resources.
Before discussing the use of the vacuum extractor it is important that the mechanisms of normal labour and childbirth are understood. There are three classical components that are described in relation to childbirth, namely, the mother's birth canal (the passage), the baby (the passenger) and the propulsive force of the uterine contractions and the expulsive force of the mother's bearing-down efforts (the powers).
Once the cervix has become completely dilated this signals the start of the second stage of labour and the birth passage is now prepared for the baby to be born when the mother's expulsive urge becomes strong. The contractions of the uterus and the mother's bearing-down efforts are the forces that propel the baby through the birth canal. At the same time the baby's head makes a series of movements that enables the fetus to move down the birth canal more easily. They include flexion (forward bending of the head), asynclitism (sideways tilting) and internal rotation (twisting of the head) before completing the birth through the outlet of the birth canal in the face-down position (occipito-anterioror OA) .
The birth canal consists of rigid bone and soft muscle tissue components which, through stretching of the latter, is transformed into a bent elastic tube down which the baby must pass. The birth canal bends through an angle of at least 90° between the inlet and outlet.
Another way the baby adjusts during the delivery process is by changing the shape of the head. This is possible because the baby's cranium is made up of a number of separate bones which can move in relation to one another and thus alter the shape of the head. This process is called moulding and is a part of the normal mechanism of labour . As the head descends into the mother's pelvis the natural forces compress the head from side to side making the cross section of the fetal head smaller and increasing the long axis. Thus the moulded head becomes ovoid or egg-shaped .
You can test for yourself how this change of shape can help the baby to deliver if you take an egg or an egg-shaped object and look at it 'end-on'. What you see is the profile with the smallest diameters in all directions. However, if you then tilt the egg you will note how the diameters you see in profile increase progressively with increasing tilt. The same principle applies to the baby's head during labour. When the head descends 'end-on' along the axis of the pelvis (flexed and synclitic), the most favourable diameters are presented to the birth canal for the birth. Obviously the chances of a normal delivery are greatest when the baby's head is in this favourable position (which is called occipito-anterioror OA) . On the other hand if the position of the baby's head is associated with some backward or sideways tilting (deflexion or asynclitism) the diameters in one or more directions will be greater than the optimum and may result in difficulty or delay in the progress of labour. This problem frequently arises when the baby's head fails to complete the normal process of internal rotation and becomes arrested in the occipito-transverse or OT position and the occipito-posterior or OP position .
The importance of the uterine contractions and the mother's expulsive efforts in achieving a normal birth (or vacuum delivery for that matter) cannot be overstated. The contractions in the first stage of labour and the contractions plus the mother's pushing in the second stage contribute to the driving force that causes the baby to move through the birth canal and eventually to be born. However, since the womb is a muscular organ, it may become exhausted during a long and difficult labour and the contractions may become weak and less effective. Fortunately, it is possible to improve the strength of the contractions by administering a hormone called oxytocin (syntocinon or pitocin) by the intravenous drip method in order to restore the contractions to a normal pattern which should then help to achieve a normal delivery.
Prolonged labour may also exhaust the mother and interfere with her ability to push during the second stage of labour. Similarly, epidural analgesia while providing effective pain relief may remove the urge to push and so reduce the mother's expulsive effort. Care must be exercised, therefore, during vacuum delivery that any reduction in the propulsive force is not replaced by extra traction force with the vacuum extractor.
The most practical way of assessing progress in the first stage of labour i.e. the part of labour before the cervix is completely open, is by estimating the extent of the cervical dilatation at regular intervals by internal examinations. The serial readings of the cervical dilatation may be plotted on graph paper M0278 to provide a visual record of the progress of labour which informs the attendant at a glance whether progress of the labour is normal or too slow. This method of assessing the progress of the labour is called a cervicograph or partograph M0287.
The vacuum extractor, sometimes called by the French name ventouse , is a device which, like the obstetric forceps, may be used to assist a woman with the delivery of her baby. Essentially all vacuum extractors consist of a cup which can be attached to the baby's scalp by suction, a traction system and a vacuum pump that provides the suction for attachment of the cup that allows the operator to assist the mother with the birth M0141.
There are many types of vacuum cups made of either flexible (soft plastic or silicone) material or rigid material (hard plastic or metal) M0040 and supplied in different designs and sizes. The reasons for these differences will be mentioned in the section (see Which type of vacuum cup should be used?). The suction pump may be a hand-held device or an electric pump. M0351
There is much more to vacuum delivery, however, than the device itself. Successful vacuum delivery depends on a number of factors all of which have to be carefully assessed before the procedure is attempted. Firstly, there has to be a good reason for undertaking the procedure such as labour progressing too slowly after the cervix has become completely dilated or there is some concern about the baby's condition. The mother should be kept fully informed of all findings and she should be involved in the management and decision-making process. The mother's participation in vacuum assisted delivery is crucial for the success of the procedure and, in addition, has a number of advantages. Not only will the mother derive satisfaction from knowing that delivery occurred largely as a result of her own efforts but the baby, too, will benefit because the greater the mother's contribution towards the birth the less will be the amount of traction necessary with the vacuum extractor to achieve delivery.
Success of vacuum extraction also depends on the clinician performing the procedure, the operator, who is usually a doctor but in some cases may be a midwife. Training in vacuum delivery includes teaching the operator how to use the instrument appropriately and correctly and how to select patients for whom vacuum delivery will be safe and successful. How the vacuum extractor is used will be described in the following sections.
Vacuum extraction may be used to assist in the delivery of the baby:
Sometimes there may be a combination of reasons that makes it necessary to expedite the delivery. On the other hand, vacuum extraction is not recommended before the cervix has become completely dilated, when the baby's head has not yet engaged or when the baby is premature.
In addition to a valid reason for delivery, there are a number of other factors that can influence the outcome which must be taken into consideration before vacuum extraction is attempted. Such factors as the overall condition of the baby and mother, the strength of the contractions, the duration of the second stage of labour, the engagement and position of the baby's head in the birth canal and the experience of the operator with the vacuum extractor.
The baby's condition may be monitored during labour by one or more of a number of clinical methods or with special tests. One of the early signs that the baby may be stressed is the appearance of a green colouration (meconium) of the amniotic fluid i.e. the fluid that surrounds the baby in the womb. The green colour is derived from the baby's bowel motions in the womb. The presence of meconium does not necessarily mean that the baby is distressed but is a warning for closer observation and monitoring. The simplest way to monitor the condition of the baby is to listen to the heart beat (auscultation) at regular intervals with a standard stethoscope or with one of the newer doppler ultrasound hearing devices.
In many hospitals, electronic fetal monitoring (EFM) (or cardiotocography - CTG) is available. This records the baby's heart rate and pattern on graph paper continuously. M0305 Before the membranes break, the EFM (CTG) is recorded from outside the mother's abdomen with ultrasound tranducers but after membrane rupture monitoring may be performed with an internal electrode attached to the infant's scalp. If all these tests are inconclusive, it is possible to test the acidity (pH) or lactate concentration of a small sample of blood taken from the baby's scalp to try to determine whether the baby's condition is deteriorating. Newer methods to assess the condition of the fetus, such as pulse oximetry and STAN technology, are currently being evaluated.
The mother's physical and emotional state, too, must be assessed before vacuum extraction is attempted. It is essential that the mother understands why delivery of the baby is required and that she should participate in the decision-making process. Alternative methods of delivery, namely forceps and caesarean section, should be mentioned and if necessary discussed in detail. If vacuum extraction is the method decided upon for the delivery, the attendant should emphasise the importance of the mother's active participation in the procedure and stress to her that the greater the maternal contribution, the less traction will be required to assist the delivery with the vacuum extractor. The mother's ability to push effectively will depend to some extent on the way she feels both physically and emotionally. Concern about the baby's condition and delay in the second stage of labour are common reasons for instrumental delivery and under these circumstances it is hardly surprising that the mother may be anxious. Some of that anxiety will be relieved if the mother and her partner are fully informed of the reasons for the operative delivery M0291 and if they receive continuous support from the attending midwife or doctor. Physical exhaustion of the mother may occur at any stage during active labour, but is more likely to occur during the pushing phase of the second stage when the extra effort of bearing down is added to the stress of contractions.
Successful vacuum extraction depends also on the presence of strong uterine contractions as well as good effort on the part of the mother. If the uterus tires and the contractions become weak, as sometimes happens during prolonged second stage of labour, the birth attendant should consider introducing the hormone oxytocin to stimulate the uterus to contract more effectively and so reduce the need for increased traction with the vacuum extractor.
If there is a strong suspicion that the baby's condition is deteriorating M0306 or if the progress of the labour is considered to be too slow M0261, assisted delivery may be necessary. Depending on the seriousness and the urgency of the obstetric situation, the choice of method of delivery will be between instrumental vaginal delivery, either forceps or vacuum extraction and caesarean section. The birth attendant will be required to analyse all the clinical information relating to the labour and, taking into consideration the wishes of the mother, decide on the most appropriate method of achieving a safe birth. How this selection procedure is performed is described in the following section.
One of the important reasons why progress in labour may be too slow is that the baby's head fails to turn completely (rotate) during descent to take up the correct position in the birth canal occipito-anterior or OA ) and may also be incompletely flexed and tilted to the side (deflexed and asynclitic). There are two classically described unfavourable head positions. When the baby's face is directed to the front in relation to the mother's pelvis the position is called occipito-posterior or OP ; and when the baby's face is directed to one or other side of the pelvis the position is called occipito-transverse or OT . These unfavourable positions result in diameters of the baby's head that may be too large to pass through the birth passage unless the position of the head can be corrected either spontaneously or with the aid of the vacuum extractor.
Thus, if the vacuum extractor is selected as the instrument to help the mother to give birth, the operator will attempt to place the vacuum cup over a precise spot on the baby's head (the flexion point ) to alter the position of the head to a more favourable one and will then help guide the head through the birth canal with correct traction technique as the mother pushes . It is important to emphasise to the mother that the aim of the vacuum extractor is to rectify the problem of the malposition of the baby's head and not merely to 'pull the baby out', thus allowing the normal mechanism of labour to complete the auto-rotation followed by delivery of the head.
The operator's experience and ability to select patients that are suitable for vacuum extraction are important factors in determining the success and safety of this method of delivery. Selection is made by assessing clinical variables that collectively may influence whether vacuum delivery is appropriate. They include the strength of the contractions, the mother's ability to push, the size of the baby and whether there are signs that the labour has become obstructed. The responsible birth attendant will proceed carefully through the following steps to determine whether a patient is suitable for vacuum extraction.
Assessment of the mother's condition
Assessment of the baby's condition - reassuring or nonreassuring
Examination of the mother's abdomen
Performing an internal pelvic examination
When the relevant information has been obtained the operator must evaluate the findings and then select the mothers who are suitable for vacuum delivery from those for whom vacuum extraction is not recommended. M0093
Since the birth canal curves through a 90° bend from inlet to outlet and because the baby's head may become stuck at different levels and in different positions in the mother's pelvis, a variety of vacuum cup designs have been introduced in an endeavour to make it possible for the operator to place the cup precisely over the correct spot on the baby's head (the flexion point) M0040 . Doing so will improve the position of the fetal head and should then allow the mother to deliver the baby with some assistance from vacuum extraction.
When the baby's head is situated low in the birth canal and in the OA position any of the cups can be used successfully because the flexion point will be readily accessible to all of them. However, when the head is higher in the mother's pelvis the same cups cannot reach the desired spot (the flexion point) because of the 90° bend in the birth canal and because the handle or suction tube on many of the vacuum cups limits the manoeuvrability of these cups. In these circumstances only specially designed cups called 'posterior' cups will be able to reach the desired spot because the flexible handle or tube can lie flat and does not prevent the cup from reaching the flexion point. One of the posterior cups should always be used when the fetal head is in either the OP (posterior) or OT (transverse) position.
In addition to differences in design, vacuum extractor cups are made of a variety of materials and each also has a specific name. The cups can be divided into two main categories, the soft cups (silicone and soft plastics) and the rigid cups (metal and hard plastics) . For your information, ask the doctor or midwife which type and name of cup was used in your baby's delivery. Soft plastic or silicone vacuum extractor cups may cause less obvious marking or swelling of the scalp than the metal or rigid plastic cups but they fail more often to complete the delivery and they detach more readily from the scalp. In addition they often cannot be applied correctly when the baby's head is in OP or OT positions for reasons discussed above.
Vacuum delivery should start with a brief explanation of the reasons for the procedure . The mother should understand that delivery will occur mainly as a result of her expulsive effort and not from traction with the vacuum extractor. The more the mother contributes to the procedure the less the operator will have to do with the vacuum extractor. Ultimately, this will benefit the baby.
The mother's legs are lifted by assistants and placed in stirrups tilted at a comfortable angle prior to washing and draping the area around the perineum. Local anaesthesia should be injected into the tissues of the perineum to make the area numb and to prevent discomfort during the insertion of the cup or if episiotomy (a cut in the perineum) is required to facilitate delivery of the baby. If the woman has received epidural analgesia, injection of anaesthetic solution into the perineum may not be necessary.
An appropriate vacuum cup is selected for the specific circumstances as previously described and is then inserted into the opening of the birth canal immediately following a contraction . The cup is then moved towards and over the flexion point on the baby's head . When the operator confirms that the cup application is correct (called flexing and median) , suction is created by using a hand or electric pump to attach the cup to the baby's scalp .
When the next contraction commences and as the mother begins to push the operator applies just enough traction in the correct direction to help the mother guide the baby through the birth canal to complete the delivery . The number of pulls required for the majority of vacuum deliveries is between three and six. However, the number of pulls will depend on a variety of obstetric factors including how effectively the mother pushes, whether she has received epidural analgesia and whether an episiotomy has been performed. The duration of the procedure from the time of application of the vacuum cup to the delivery of the baby is usually completed within 15 minutes and should rarely last longer than 20 minutes. Most vacuum deliveries are completed well before this time.
The following list contains most of the vacuum extractor cups that are commercially available at the present time. For more information, ask your doctor or midwife which of the cups are used in your hospital then click on that particular cup to see what it looks like and for a brief animated sequence of how it is used for a vacuum delivery.
After the baby has been born, the operator should examine the baby's head as soon as possible M0353 to check that no injury has occurred to the scalp and to reassure the parents that the swelling caused by the cup (called the chignon or artificial caput ) will subside after several hours and that any marking resulting from the cup's attachment will disappear over a few days. On the day following the vacuum delivery the operator should reexamine the baby in the mother's presence to check the vacuum cup's application site on the scalp and to inform the mother of the reasons and details of the procedure and to answer any questions that she might have about the birth M0311.
Some babies display a varying degree of irritability following vacuum delivery but this irritability may be related to the condition of the baby prior to the vacuum extraction as well as to the way the instrument was used. Most irritable behaviours are transient and are no longer detectable a day or two after the birth.
All vacuum extractor cups depend for their action on a firm attachment by suction to the baby's scalp . For this reason, all of them will cause a swelling of the scalp (a chignon) which is harmless and which will resolve in a matter of hours. Similarly, a circular cup mark will always be present at the site of cup attachment but the extent to which it is visible will depend on the amount of hair present on the scalp . If the baby is born with a sparse covering of hair the marking will be most obvious and easily visible whereas it may be hardly noticeable in babies with thick hair. Such markings disappear after a few days without leaving any traces on the scalp.
Occasionally the colour of the swelling (chignon) may be quite dark at first but will fade quickly and disappear usually by the fourth day . For this reason they should not be regarded as injuries or bruises because such terms will only raise the mother's anxiety levels. Birth attendants should be conscious of this and make it their practice to reassure the parents about the transient nature of the cosmetic effects such as cup marks and swelling. During the procedure and before the cup is removed from the scalp parents should be forewarned of the appearance of the chignon and reassured as to its benign nature.
Blisters and abrasions of the scalp may sometimes occur during vacuum extraction . The majority are small in size and superficial but occasionally they may be more extensive. Blisters tend to occur when there is only a sparse covering of hair on the scalp and the extraction is prolonged while abrasions tend to occur when the delivery is difficult especially if the cup detaches from the scalp. Blisters and superficial abrasions will heal completely after a few days; large abrasions, however, may take a week or ten days to heal but parents can be reassured with confidence that they will eventually heal without leaving any traces on the scalp , . Soft vacuum extractor cups made of silicone or soft plastic materials appear to cause less marking and fewer abrasions of the scalp but they are less likely to succeed to complete the delivery than the rigid cups and they are not associated with fewer serious injuries.
A cephalhaematoma is another scalp effect that may be seen after vacuum extraction. It is a small collection of blood that accumulates under the deepest layer of the scalp (the periosteum ) to form a soft but discreet lump on the baby's head M0302 . They can occur after normal delivery but are more common after vacuum extraction . Cephalhaematomas are almost always harmless to the infant and resolve spontaneously although the larger ones may take a few weeks to disappear. No specific treatment is required and the parents should be reassured accordingly. Mild jaundice appears to be more common after vacuum delivery than after normal or forceps delivery but not the clinically significant type of jaundice that requires treatment under light (phototherapy).
More serious injuries that are very occasionally associated with vacuum assisted delivery are subgaleal haemorrhage (SGH) and intracranial bleeding (ICH). A subgaleal haematoma is formed when bleeding occurs into the space between the scalp and the cranium M0303. Small SGH occur in around 1-2 per cent of vacuum extractions but they usually resolve completely over a few days without any specific treatment. Large SGH are much less common but can be clinically serious for the infant and these babies require careful observation and prompt treatment if their condition deteriorates. However, even large SGH will resolve within a week and, in the long term the infant will be normal provided no other injury was sustained during the birth. Although SGH may also occur after normal or forceps delivery or if the baby suffers from a bleeding disorder the majority are associated with vacuum extraction where the procedure is reported to be difficult. Intracranial injury has been reported to occur in about one in a thousand vacuum deliveries and is more common with difficult and failed extractions . However, the incidence of ICH following vacuum extraction is not greater than that of forceps delivery or caesarean section performed during labour.
Serious injury to the baby associated with vacuum delivery can usually be avoided or reduced to a minimum if careful attention is paid to a number of safety measures that should always be strictly adhered to and enforced. These measures may be addressed before and during vacuum extraction and a few may be instituted after the delivery has been completed.
The operator should select only those patients who are suitable for vacuum delivery and carefully assess the obstetric circumstances to ensure there are no adverse factors that would contraindicate the procedure . An appropriate vacuum cup should be chosen to enable the operator to achieve a correct application over the flexion point on the baby's head . During the delivery the mother should be urged to push with maximum effort and traction should only be applied to the cup when the mother is pushing. Excessive traction should be avoided and detachment of the cup from the scalp should be prevented . Traction should be directed along the axis of the mother's pelvis (axis traction) . It is important to emphasise that birth should occur mainly as a result of the mother's expulsive efforts and complemented to a lesser extent by traction with the vacuum extractor . The more the mother contributes to the birth, the less the operator has to pull on the device and the better will it be for the baby.
Immediately after vacuum delivery the baby should be carefully examined for any signs of injury and if some injury is detected appropriate treatment should be commenced promptly. The mother should be kept informed about the baby's condition and about the relevant details of the procedure and any questions or concerns she may have about the birth should be addressed M0312.
When a baby requires delivery before the cervix reaches complete dilatation, caesarean section is the only reasonable option. However, after the cervix has become completely dilated the choice of method will be between instrumental vaginal delivery, either vacuum extraction or forceps, and caesarean section depending on the obstetric circumstances that exist and to some extent on the preference of the mother. In addition, the choice of method may be determined by the experience and skill of the operator with one or other method.
There is much debate in the medical literature about whether vacuum extraction or forceps delivery is preferable for the mother or baby. Care should be exercised when comparing results of forceps delivery and vacuum extraction because there are many factors to be considered besides the instruments themselves and because the respective techniques for using them are quite different. Training in one method does not necessarily cross over to the other so it is important that the operator is familiar with the instrument that is being used. A forceps delivery that is performed well is preferable to a badly performed vacuum extraction and vice versa. From the mother's point of view vacuum delivery is associated with less injury to the birth canal than the forceps. Nevertheless, injury can occur to the genital tract with difficult deliveries or if failure of vacuum extraction is followed by attempted forceps delivery. From the baby's perspective the situation is not so clear cut and each has the potential for injury to the infant if safety limits are transgressed. Reviews of follow-up studies of babies born after forceps and vacuum extraction have shown that intellectual impairment was rare except when there was significant hypoxic injury associated with a difficult delivery. Similarly no differences were found in the long term development of babies who had been born during studies comparing forceps and vacuum extraction.
There are also changing trends and divergent views about the place of caesarean section in current obstetric practice, some of it brought about by a more liberal attitude towards maternal requests for elective caesarean births. The issues behind these changes include, on the one hand, the mother's desire to avoid injuries to the genital tract and their potential long term consequences of bowel and urinary disturbances and, on the other, the possibility of injury to the fetus with operative vaginal delivery. With regard to the latter, avoiding difficult deliveries and strictly adhering to safety precautions should prevent most of the serious problems associated with vacuum extraction provided the baby is healthy at the start of the procedure.