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Labour and Delivery After Previous Caesarean
Once a Caesarean Always a Caesarean
‘One thing must always be borne in mind, viz., that no matter how carefully a uterine incision is sutured, we can never be certain that the cicatrized uterine wall will stand a subsequent pregnancy and labor without rupture. This means that the usual rule is, once a Caesarean always a Caesarean. Many exceptions occur … The general rule holds, however, that we cannot depend upon a sutured uterine wall, whether it is done in a Caesarean section or a myomectomy, hence I believe the extension of Caesarean section to conditions other than dystocia from contracted pelvis or tumours should be exceptional and infrequent.’ Edwin CraiginConservatism in obstetrics. NY Med J. 1916;104:1–3.
One of the most common dictums in obstetrics was put forward almost a century ago by Edwin Craigin: ‘once a caesarean always a caesarean’. The main purpose of Craigin’s presentation was to point out the maternal risks of the first caesarean section with a plea that it should be used only for the most stringent indications. In the early 20th century the most common indication for caesarean section was disproportion and contracted pelvis, and the type of caesarean section was classical with its associated significant risk of uterine rupture in a subsequent pregnancy. Thus, when Craigin proposed his dictum it was appropriate, as it would be now under the same circumstances. Craigin’s main point was that caesarean section was a dangerous operation and that once it was performed, the woman would be subject to the dangers of repeat caesarean section in a subsequent pregnancy. He did, however, point out that vaginal delivery after previous caesarean section was feasible and reported one of his own patients who had three vaginal deliveries after one caesarean section.
As the low transverse caesarean section became more common in the 1930s and 1940s, and the indications for caesarean section widened to include nonrecurrent reasons, the approach to women previously delivered by caesarean section changed in many countries. The risk of subsequent rupture of low transverse caesarean section was small and increasing numbers of women were encouraged to undergo labour and vaginal delivery. By the late 1970s and 1980s, there were many reports of large series showing that spontaneous labour and vaginal delivery following a single low transverse caesarean section was a safe and reasonable option with appropriate safeguards. Consensus statements embraced and encouraged labour and vaginal delivery with a previous caesarean section under these circumstances.
However, as is so often the case in obstetrics, the pendulum of opinion swings too far and labour and vaginal delivery were pursued for widening indications – including more than one previous caesarean section, induction of labour and acceleration with oxytocin of nonprogressive labour. Not surprisingly, an increasing number of cases of uterine rupture were reported, some of which resulted in fetal death or severe neonatal neurological damage, as well as maternal morbidity, sometimes including hysterectomy. The possibility of complete uterine rupture in labour ranges from 3 to 7 per 1000 pregnancies, while the risk of perinatal death or severe morbidity, should rupture occur, is 4.5 per 1000 more with trial of vaginal delivery than with repeat caesarean delivery. These rare but tragic outcomes and the associated medicolegal sequelae caused the pendulum to swing rapidly back in the opposite direction. Revised national guidelines suggested more stringent facility and personnel requirements to conduct labour and vaginal delivery following previous caesarean section. Some hospitals, fearing institutional liability, forbade labour and vaginal delivery following previous caesarean section. The most sensible, practical and safest clinical course lies in the middle ground.
This chapter will outline the factors that need to be considered in helping women reach a decision whether or not to undertake labour with a view to vaginal delivery after previous caesarean section.
Selection Criteria for Vaginal Birth After Caesarean Section (Vbac)
The previous obstetrical record should be reviewed so that details of the labour, indications for caesarean section, operative details and postoperative recovery can be appraised. There are several factors that need to be evaluated in assessing the level of medical risk and, indeed, medicolegal risk, so that the appropriate informed consent can be obtained. It is also important to realize that there is not always professional or maternal consensus about all or any of these factors.
Type of Uterine Scar
The most important consideration and where there is most agreement is the consideration of the type of uterine scar, intraoperative complications and the number of previous scars.
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Classical caesarean section scars are about 10 times more likely to rupture during labour than lower segment caesarean incisions and may rupture before the onset of labour. The rupture rate for a previous classical scar is approximately 3–5%.
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Low vertical caesarean section is rarely performed in modern practice. The indication is usually in earlier gestation when the lower uterine segment has formed to a degree but its transverse dimensions are felt to be inadequate for the normal transverse incision. In these cases the low vertical incision has been advocated as an alternative to classical caesarean section. However, in many instances the lower segment is not sufficiently developed, even vertically, to allow a big enough incision without encroaching on the upper uterine segment. Thus, these scars, while having a slightly smaller risk of rupture than a classical caesarean scar, are probably best treated in the same manner.
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Extensions of a transverse lower segment caesarean incision should be appraised by careful scrutiny of the operative report. If there was any marked extension of one or both angles, or a ‘T’ extension into the upper uterine segment, many believe that these scars should not be subjected to labour. Unfortunately though, there are no objective criteria for determining which may be suitable.
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Hysterotomy scars are not commonly seen in modern obstetrics with medical methods for second trimester termination. However, if present they should be treated in the same manner as a classical caesarean scar and repeat elective caesarean section chosen.
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Myomectomy incisions require individual consideration. If the incisions are extensive, and possibly more so if the uterine cavity was entered, they are best not subjected to labour. Similarly, hysteroscopic myomectomy incisions, if associated with perforation of the uterus, would be best managed by elective caesarean section. Otherwise, hysteroscopic myomectomies not associated with perforation or deep myometrial excision can be allowed to labour. Again the evidence is not clear on any of these subtle variations.
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Previous rupture of any type of uterine scar in a previous pregnancy is obviously a contraindication to subsequent labour.
In some cases, it is impossible to obtain the previous operative record. From the history, it is often possible to work out the type of the previous uterine incision. For example, if the previous caesarean section was done at term, and particularly if it was for dystocia, one can reasonably assume that it was a transverse lower segment caesarean section. However, if the caesarean section was done at less than 32 weeks’ gestation and not in labour, there is a chance that a classical caesarean section was done. Acceleration of labour with oxytocin with an unknown uterine scar is associated with an increased risk of uterine rupture and dehiscence.
Labour With the Previous Caesarean Section
It is important clinically to distinguish between women who have either had a previous vaginal delivery as well as a caesarean section, those who have laboured and had a caesarean section intrapartum and those who have only had a previous prelabour caesarean section. However, although the outcomes and chances of successful vaginal delivery may be different, there are compelling arguments for managing them the same way in labour because the unpredictable risk of rupture remains the same.
Uterine Incision Closure
One large retrospective review showed a significant increase of subsequent scar rupture in those women in whom the initial caesarean had a single-layer versus a double-layer closure. However, this finding has not been noted in other hospitals and there are many who have not shown an increase in scar rupture rates or changes in infectious morbidity since changing to single-layer closure.
Postoperative Infection
Postpartum endomyometritis may interfere with adequate healing of the uterine scar and increase the risk of subsequent rupture in labour. The practical clinical point though is that many cases of postpartum fever are not due to endomyometritis. Thus, it is inappropriate to exclude all women who have had a postpartum fever following the previous caesarean delivery. However, if there is good clinical evidence in the record that the sepsis was intrauterine, it may be prudent to avoid labour in a subsequent pregnancy.
Recurrent Indications for Caesarean Section
One of the reasons for the first caesarean section is often dystocia or cephalopelvic disproportion, although a true diagnosis of the latter is rare. These diagnoses are not necessarily a recurrent indication and the majority will labour and deliver successfully after a previous caesarean for these indications, sometimes even with a bigger baby. Overall, however, they may have a slightly lower success rate than for other ‘nonrecurrent’ indications.
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