Common Questions about VBAC birth
By Dr. David Simon.
It has been said that VBAC depends far more on
mental, emotional and spiritual factors than physical factors1,
but having up to date medical information can help in deciding what
is right for you and your baby.
What are my chances of birthing vaginally if
I've had a Caesar?
Most studies suggest successful VBAC rates of 60- 80%, or three
to four out of five, in those who try. Most women currently in Australia
do not try for VBAC, or are not permitted to, so the overall VBAC
rate in Victoria was only 22% in 1999.2
What if I had 'failure to progress' or 'CPD'
last time?
There is still at least a two-thirds chance (67%) of vaginal birth
if you try VBAC 3. This continues
to be true even when CPD is defined by strict conditions including
that the baby was not posterior, the cervix was dilated at least
5 cm and labour was not responsive to oxytocin
4. Even if you needed a caesarean at fully dilated for an
unsuccessful forceps or vacuum birth you still have up to a 75%
chance5. Each labour is different.
What if I've previously had a vaginal birth
as well as a caesarean?
You are in the group of VBAC women with the highest (85-93%) chance
of vaginal birth, and the lowest chance (0.2% or 1 in 500) of uterus
rupture 6, 7.
Are there situations where the risk of rupture
is higher?
Yes - a 'classical', or up and down uterus scar has a 2 to 10 fold
risk of rupture and a 5 to 10 fold risk of maternal or baby death8
This type of scar is also more likely to rupture prior to labour
than a lower segment scar. J or T incisions are thought to have
a similar risk of rupture as classical scars.
Can I be induced if I have had a previous caesarean?
An early VBAC study suggested that scar dehiscence rate was not
significantly increased when oxytocin was used for induction or
augmentation9, and a further
review found a similar finding as long as an epidural wasn't also
used10. More recent studies
have not been as reassuring. One US series showed an almost five-fold
increase in uterine rupture with oxytocin induction compared to
no oxytocin use11 whilst
European experience also suggests caution12,
13. A recent report cautions that induction with prostaglandin
(the gel) may put the risk of rupture as high as one in 4014.
In this study there was a modest increase in the risk of uterine
rupture when labour was induced without prostaglandin to 0.77% (one
in 130), compared to 0.52% (one in 192) when labour started spontaneously.
If there is a strong reason to justify induction of labour, you
must consider this increased risk when deciding what is right for
you. If labour really must be induced, you could try just breaking
the waters first.
Can I have an epidural if I need one during
my VBAC?
Uterus rupture rate may be increased significantly13,
but perhaps only if oxytocin is also used12.
Another study that had an epidural rate of 75% with VBAC, however,
showed no increased chance of scar rupture in those women who chose
epidural11. Sometimes an
epidural is the only way to continue with a labour that is really
difficult for you. Good antenatal preparation for labour and good
support people may be really important here. It is important to
note that these are not randomised controlled trials, and it may
be that the women who need epidurals are the ones who also have
increased risk of rupture for, as yet, undefined reasons. We cannot
say that the epidural is the cause of the increased rupture rate.
Pain does not reliably indicate uterine rupture, so an epidural
is not contra-indicated. It would be wise, however, to have continuous
monitoring if an epidural is placed.
Why does my doctor suggest continuous CTG monitoring?
A continuous CTG monitor (reading of baby's heart beat) is said
to give the best indication of uterus rupture8
and nearly all reported studies on the safety of VBAC have used
continuous monitoring. It is usually part of the VBAC protocol in
Australian hospitals. In the rare event of uterine scar rupture,
the danger to mother or baby is somewhat dependent on how quickly
emergency action is taken15.
There is no 'proof' that it is necessary, however, and being connected
to the monitor can sometimes interfere with freedom of movement
in labour. The Canadian Society of Obstetricians and Gynaecologists
(SOGC) recommendations for VBAC suggest, 'In cases of induction
and/or augmentation, continuous electronic foetal heart rate monitoring
is advised. Intermittent foetal heart rate monitoring is to be reserved
for cases in which neither induction nor augmentation with oxytocin
is performed'16. It is very
important not to let a CTG monitor be replacement for one-on-one
midwifery care in your labour.
Why do I need a drip in VBAC?
The rationale for the insertion of the bung is to prevent any delay
in instituting emergency management in the rare event of uterine
rupture. An anaesthetist needing to give an emergency anaesthetic
would take less than a minute to insert an IV line. One could argue
that this is not a significant delay when considering the time needed
to get a caesarean organised, and considering the rarity of rupture.
You may be able to negotiate this with your doctor.
I have had two previous Caesars - can I try
for VBAC?
Many studies of women with more than one previous caesarean have
been reported now9, 17-20.
The risk of uterine rupture has varied from 0.7% (one in 142), the
same as with one previous caesarean, up to 3.7% (one in 27). The
chance of vaginal birth tended to be lower than after only one previous
caesarean, but still as high as 65-75%. One study aptly summarised
their experience: "Although patients with 2 prior caesareans should
be counselled differently from patients with 1 prior caesarean scar
about the increased risk of uterine rupture and decreased chance
of vaginal delivery in a subsequent trial of labour, on the basis
of evidence from this study and the existing literature, motivated
patients may still wish to undergo a trial of labour".
What if my baby is breech?
Up to a quarter of babies are breech (bottom first) early in the
third trimester (last 12 weeks). Most will turn by themselves, so
be patient. External cephalic version (ECV) is a technique used
to gently turn the baby and has been shown to decrease the need
for caesarean or vaginal breech birth by half21.
ECV can be used if you have had a previous caesarean but you will
need to talk in detail to your carer about the possible risks. Limited
data suggests that serious complications are rare22,
23. Most of the major teaching hospitals would offer an ECV
service if your carer is not experienced with the technique. There
is some reported experience of vaginal breech birth after caesarean24,
25, but you should also discuss the recent 'Term Breech Trial'
with your carer26. The study
and an editorial comment can be read on-line by using the address
below.
What if my baby is thought to be big (macrosomic)?
A study found somewhat lower successful VBAC rates of 58% for those
babies weighing 4000-4499g and 43% in those over 4500g 27
but no significant difference in baby or mother morbidity (injury
or sickness) when compared to VBAC with babies under 4000g, or when
compared with women with macrosomic babies but with no uterine scar.
There is also the problem that ultrasound is not particularly accurate
at determining the weight of larger babies 28.
The guidelines of the SOGC suggest "Published information does not
suggest that a diagnosis of suspected macrosomia is a contra-indication
to labour after previous low segment Caesarean section" 16.
So, is VBAC safe?
Neither elective Caesar nor VBAC nor normal birth is without risks
to mother and baby though, for most, serious complications are rare.
No one can predict with certainty the outcome in any individual.
You should seek out information from a variety of sources ->
midwife, obstetrician, books, and other women - weigh up the risks,
look at your own special situation, then make your plan for your
birth.
To find out how to obtain a free copy, or how you
can organise to distribute the booklets, please click
here.
