In case of a previous caesarean section, a subsequent pregnancy can be planned to be delivered by either of the following two main methods: Vaginal birth after caesarean section (VBAC) Elective repeat caesarean section (ERCS)
Both have higher risks than a vaginal birth with no previous caesarean section. There are many issues which affect the decision for planned vaginal or planned abdominal delivery. There is a slightly higher risk for uterine rupture and perinatal death of the child with VBAC than ERCS, but the absolute increased risk of these complications is small, especially with only one previous low transverse caesarean section. A large majority of women planning VBAC will achieve a successful vaginal delivery, although there are more risks to the mother and baby from an unplanned caesarean section than from an ERCS. Successful VBAC also reduces the risk of complications in future pregnancies more than ERCS.
In 2010, the National Institutes of Health, U.S. Department of Health and Human Services, and American College of Obstetricians and Gynecologists all released statements in support of increasing VBAC access and rates. Recently, it is recognized that as the number of cesarean sections a patient undergoes increases so does the risk of significant obstetrical complications It is still suggested to try VBAC over ERCS even with its slightly higher risk of uterine rupture.
TOLAC (trial of labor after caesarean) is an attempt at vaginal delivery to see whether it can succeed in resulting in a VBAC. If it turns out not to progress acceptably, then a caesarean is performed.
Technique Where the woman is labouring with a previous section scar (i.e. a planned VBAC in labour), depending on the provider, special precautions may be recommended. These include intravenous access (a cannula into the vein) and continuous fetal monitoring (cardiotocography or CTG monitoring of the fetal heart rate with transducers on the mother's abdomen). Most women in the UK should be counselled to avoid induction of labour if there are no medical reasons for it, as the risks of uterine rupture of the previous scar are increased if the labour is induced. Other intrapartum management options, including analgesia/anesthesia, are identical to those of any labour and vaginal delivery.
For ERCS, the choice of skin incision should be determined by what seems to be most beneficial for the present operation, regardless of the choice of the previous location as seen by its scar, although the vast majority of surgeons will incise through the previous scar to optimise the cosmetic result. Hypertrophic (very thick or unsightly) scars are best excised because it gives a better cosmetic result and is associated with improved wound healing. On the other hand, keloid scars should have their margins left without any incision because of risk of tissue reaction in the subsequent scar.
Selection criteria The choice of VBAC or ERCS depends on many issues: medical and obstetric indications, maternal choice and availability of provider and birth setting (hospital, birthing center, or home). Some commonly employed criteria include:
Factors favoring VBAC If the previous caesarean(s) involved a low transverse incision there is less risk of uterine rupture than if there was a low vertical incision, classical incision, T-shaped, inverted T-shaped, or J-shaped incision. A previous successful vaginal delivery (before or after the caesarean section) increases the chances of a successful VBAC. The indication for the previous caesarean section should not be present in the current pregnancy. The prior cesarean was due to a non-recurring condition such as breech presentation. Location at an institution equipped to respond to emergencies with physicians immediately available to provide emergency care.
Factors favoring ERCS The more caesarean sections that a woman has had, the less likely she will be eligible for VBAC. VBAC after two or more prior lower uterine segment transverse CS is controversial. The Royal College of Obstetricians and Gynaecologists recommends that women with a prior history of even two previous uncomplicated low transverse Caesarean sections, in an otherwise uncomplicated pregnancy at term, with no contraindication for vaginal birth, may be considered suitable for planned VBAC. The presence of twins may reduce the chance of successful VBAC, but if the leading twin is head first (cephalic presentation) and there are no other reasons to recommend caesarean section, VBAC should be offered. The prior cesarean was due to a condition likely to recur such as arrest of labor. VBAC may be discouraged if there are other medical complications but this will require an individualised assessment and discussion between the woman and her obstetrician. There is less likelihood of achieving successful VBAC if any of the following factors are presents: labor induction or augmentation, advanced maternal age, high body mass index, high birth weight, gestational age greater than 40 weeks, short interdelivery interval (less than 19 months), and preeclampsia.
According to ACOG guidelines, the following criteria may reduce the likelihood of VBAC success but should NOT preclude a trial of labour: having two prior caesarean sections, suspected fetal macrosomia at term (fetus greater than 4000-4500 grams in weight), gestation beyond 40 weeks, twin gestation, and previous low vertical or unknown previous incision type, provided a classical uterine incision is not suspected.
Criteria where ERCS should be performed The presence of any of the following practically always mean that ERCS will be performed – but this decision should always be discussed with a senior obstetrician: Maternal request for elective repeat CS after counselling Maternal or fetal reasons to avoid vaginal birth in current pregnancy Previous uterine incision other than transverse segment including classical (longitudinal). The Royal College of Obstetricians and Gynaecologists recommends that women with a prior history of one classical (longitudinal) caesarean section should give birth by elective repeat caesarean section (ERCS). Unknown previous uterine incision Previous uterine rupture. For women with a history of prior uterine rupture, ERCS should be performed before the onset of spontaneous labor. A planned cesarean is generally recommended between 36 weeks and 37 weeks of gestation for these patients according to updated guidance by ACOG in 2019. Previous hysterotomy or myomectomy where the uterine cavity was breached
Outcomes in VBAC versus ERCS VBAC and ERCS differ in outcomes on many end-points.
The American College of Obstetricians and Gynecologists (ACOG) states that VBAC is associated with decreased maternal morbidity and a decreased risk of complications in future pregnancies than ERCS. However, an unplanned cesarean section following a TOLAC is associated with increased complications compared to both ERCS and successful VBAC.
According to the American College of Obstetricians and Gynecologists (ACOG), it is most appropriate to compare the clinical and statistical risks for elective repeat cesarean section (ERCS) with trial of labor after cesarean (TOLAC) given that a successful vaginal birth after cesarean (VBAC) is never guaranteed and complications are primarily associated with failed TOLAC.
Uterine rupture A caesarean section leaves a scar in the wall of the uterus which is considered weaker than the normal uterine wall. A VBAC carries a risk of uterine rupture of 22–74/10,000. Slightly lower risk of uterine rupture in women undergoing ERCS (i.e. a section before the onset of labour). Mothers with a previous lower uterine segment cesarean are considered the best candidates for VBAC, as that region of the uterus is under less physical stress during labor and delivery. Although there is higher risk of uterine rupture in VBAC than ERCS, both rates happen to be very low. Sometimes no significant difference in uterine rupture rates is found between the groups of VBAC and ERCS. If a uterine rupture does occur, the risk of perinatal death is approximately 6%. Even if it happens, most birthing parents and babies will recover completely after uterine rupture.
Risks to the child A VBAC carries a 2–3/10,000 additional risk of birth-related perinatal death when compared with ERCS. The absolute risk of such birth-related perinatal loss is comparable to the risk for women having their first birth. Planned VBAC carries an 8/10,000 risk of the child developing hypoxic ischaemic encephalopathy, but the long-term outcome of the infant with HIE is unknown and related to many factors.
On the other hand, attempting VBAC reduces the risk that the child will have respiratory problems after birth such as infant respiratory distress syndrome (IRDS), as rates are estimated at 2–3% with planned VBAC and 3–4% with ERCS.
Conversion from planned VBAC to Caesarean For women who have previously had a Caesarean, VBAC rates have ranged from 5% in 1985 to 23.8% in 1996 to 8.5% in 2006 in accordance with professional recommendations at the time. However, of the women that opt for a TOLAC, between 60%–80% will successfully give birth vaginally, which is comparable to the overall vaginal delivery rate in the United States in 2010.
The chance of having a successful VBAC is decreased by the following factors: Labor induction No previous vaginal birth Body mass index greater than 30 Previous caesarean for obstructed labour No epidural anaesthesia Previous preterm caesarean birth Cervical dilation at admission to labour ward less than 4 cm Less than 2 years from previous caesarean birth Advanced maternal age Support from hospital, care provider, and staff When the first four factors are present, successful VBAC is achieved in only 40% of cases. In contrast, in women with a previous caesarean section who have had a subsequent vaginal birth, the chance of a successful vaginal birth again is estimated at 87–90%.
Risks in future pregnancies ERCS, as compared to VBAC, further increases the risks of complications in future pregnancies. Complications whose risks significantly increase with increasing number of repeated caesarean sections include: Placenta accreta, estimated to be present in 0.2%, 0.3%, 0.6%, 2.1%, 2.3% and 6.7% of women undergoing their first, second, third, fourth, fifth, and sixth or more caesarean sections, respectively. According to the United States Agency for Healthcare Research and Quality, "Abnormal placentation has been associated with both maternal and neonatal morbidity including need for antepartum hospitalization, preterm delivery, emergent caesarean delivery, hysterectomy, blood transfusion, surgical injury, intensive care unit (ICU) stay, and fetal and maternal death and may be life-threatening for mother and baby." Hysterectomy, estimated to be performed in 0.7%, 0.4%, 0.9%, 2.4%, 3.5% and 9.0% of women undergoing their first, second, third, fourth, fifth, and sixth or more caesarean sections, respectively Injury to bladder, bowel or ureter Ileus The need for postoperative ventilation Intensive care unit admission Blood transfusion requirement, estimated at 7%, 8% and 14% with a history of two, three and five caesarean births, respectively. Duration of operative time and hospital stay.
Other Aside from uterine rupture risk, the drawbacks of VBAC are usually minor and identical to those of any vaginal delivery, including the risk of perineal tearing. Maternal morbidity, NICU admissions, length of hospital stay, and medical costs are typically reduced following a VBAC rather than a repeat caesarean delivery.
A VBAC, compared with ERCS, carries around 1% additional risk of either blood transfusion (mainly because of antepartum hemorrhage), postpartum haemorrhage or endometritis.
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