Caesarean section is a common surgical procedure. Up to one woman in four in Australia has a baby delivered by caesarean section. For decades it had been generally assumed that once a woman had a caesarean section, all her future babies would have to be delivered by caesarean section.
However, this concept has changed due to improvements in obstetric care and surgical techniques. Many women who had a caesarean section can safely give birth through the vagina during a subsequent labour. This is known as vaginal birth after caesarean section (VBAC). With careful selection of patients and good obstetric care, from five to eight women out of 10 who attempt VBAC are successful.
Reasons for Vaginal Birth After Caesarean Section
- Lower risk of complications (such as bleeding and infection) than routine, repeat caesarean section.
- Other risks associated with surgery are avoided, such as a reaction to the anaesthetic, damage to internal organs, decreased bowel function, and abdominal wound infection.
- A shorter hospital stay and a quicker recovery.
- Some women regard vaginal birth as more fulfilling.
- If successful, VBAC facilitates vaginal birth of subsequent babies, avoiding the risks of repeat caesarean section.
When all risks of labour and birth are considered, VBAC for an appropriately selected woman has fewer risks of complications than routine, repeat caesarean section. However, VBAC does have small but significant risks for the mother and baby.
The Decision to Attempt VBAC
The decision to attempt VBAC is best made in discussion with your doctor. It will depend on your medical history and the progress of your current pregnancy. While you have the right to make a decision to attempt VBAC, ultimately your doctor must decide whether or not an attempt is safe. To decide your doctor will consider factors such as:
- The location of the uterine scar from caesarean incision
- The reason for previous caesarean section is still present
- How you want to deliver this baby
- Your access to a hospital that is well equipped for an emergency caesarean section
- How many more babies you hope to have
- The time since your previous caesarean section (uterine scars less than two years old may have greater risk of rupture).
Location of the uterine scar: The women most suitable for VBAC have had a horizontal incision (cut) in the lower part of the uterus, known as a lower transverse uterine incision.
The four types of uterine incisions are:
- Lower transverse- a side-to-side cut in the lower, thinner part of the uterus where labour contractions are minor, this is the most common incision and is the most suitable for subsequent VBAC.
- Low vertical- an up-and-down cut in the lower thinner part of the uterus.
- High os ‘’classical’’ – an up-and-down or horizontal cut in the upper part of the uterus; more stress is places on this area during labour than on the lower areas of the uterus.
- Inverted ‘’T shape’’ incision; this is the weakest scar.
You cannot tell where your uterine scare is by looking at the scar on your skin. The uterine scar is in a different position. A doctor needs to see your medical records to determine which type of uterine incision was made. Another factor is whether the reason for your previous caesarean section is again present in your current pregnancy. If the problem is absent VBAC might be an option.
Preparing for Vaginal Delivery
Some women are enthusiastic about attempting VBAC, while other may be reluctant, especially if prior caesarean section was performed in emergency. Discuss your concerns fully and frankly with your doctor because understanding labour and its stages can be helpful. Remember: when you attempt a VBAC you may still need a caesarean section if a complication arises.
Epidural analgesia can be used during VBAC. However, it may limit mobility and make it more difficult to push the baby out. Other pain-relief medications such as pethidine can be used or non-drug techniques such as massage or emotional support.
Unsuitable conditions for VBAC
- The woman has a ‘’classical’’ scar or inverted-T uterine scar.
- The position of the uterine scar is unknown.
- The woman does not want to try a vaginal delivery.
- Some types of previous uterine surgery, such as fibroid removal.
- Previous rupture of the uterus.
- The woman needs induction of labour and has an unfavorable cervix.
- The woman has an unusual pelvic shape.
- The baby is in the transverse position (lying across the uterus).
- The baby appears to be too big to pass through the birth canal.
- The hospital where you want to deliver is not equipped for an emergency caesarean section.
- The woman has a medical condition that can complicate labour.
- Any other contradictions to labour (for example, placenta praevia, where the placenta lies across the cervix).
There can be other medical reasons why VBAC may not be safe for a woman, and they may be unrelated to the previous caesarean section.
Risks of VBAC
VBAC is associated with a small risk of rupture of the uterine scar. This rupture can be caused by the uterus’s forceful contractions during labour and pressure against the scar. Rupture of a uterine scar is uncommon but serious complication.
The signs of uterine rupture can be difficult to detect. A woman may have some bleeding or pain between contractions, but changes in the baby’s heart rate may be the first sign of a uterine rupture. This is why continuous electronic monitoring of the baby is often recommended during VBAC. Rupture of the uterine scar can be life-threatening for mother and baby, and an emergency caesarean section will be necessary. Rupture of the uterine occurs about once in every 200 VBAC attempts. Of those women who do have a rupture during VBAC:
- About one woman in 10 of these women will need a hysterectomy (uncommonly, a woman may need a hysterectomy following uncontrollable bleeding during an elective caesarean section)
- About one birth in 10 result in stillbirth.
Of every 10 women who attempt VBAC, from two to five will need to have a repeat caesarean section. For this only reason VCAB should take place only in the hospital equipped to perform and emergency caesarean section. In an emergency, general anesthesia or regional (spinal or epidural) anesthesia will be required, depending on the situation at the time.
The most common reason for an emergency caesarean section during VBAC is not uterine rupture but failure of the labour progress. Any labour is associated with some risk to the baby. It has been estimated that, during VBAC, risks to the baby are similar to those who faced by a baby who is the vaginal first-born to any mother.