We are due our second child in February next year (a 20-month gap between no.1 and no.2 – yes, I’m weary just thinking about it). I shall spare you the warts-and-all birth story, but our first baby was born by caesarian section after a worrying dip in his heart rate.
There are two options for women in this situation. The first is to choose to have a caesarian delivery again, which is known as “elective repeat caesarian delivery”, or ERCD for short. The second is to have a “vaginal birth after caesarian”, often abbreviated to VBAC. The actual process of attempting a VBAC is called “trial of labour after caesarian”, or TOLAC.
If we were living forty years ago, there wouldn’t be much debate – we would have been booked in for a C-section. This started to change in the 1980s as more women and couples pushed to have a more ‘natural’* vaginal birth, which led to an increasing number of VBACs. This was backed by improving caesarian surgery, such as a change from making the incision ‘up’ the belly (‘longitudinal’) to making it ‘across’ the belly (‘transverse’) to achieve more effective repair, as well as advice from leading health organisations to reduce caesarian rates.
It seems that in the UK, however, as in many other countries, caesarian deliveries after previous caesarians are back on the increase. One reason is the real fear that the uterus, weakened by the surgery, even by a transverse section, might rupture if a vaginal birth is attempted. A ruptured uterus can lead to complications for the mother and child (more on the specifics in a minute).
There are currently no randomised trials to compare the risks associated with two approaches and most studies have looked retrospectively at what happens in ERCDs or VBACs. This means that it’s hard to inform women before they give birth what the different risks might be.
An article in the scientific journal PLOS Medicine earlier this year – ‘To VBAC or Not to VBAC‘ by Catherine Spong - summarised two research papers that were published at the same time. They both capture information on what the mother intended to do, as well as what actually happened. This gives some relevant insight into whether preferences were successfully carried out, and what the true risks are for women planning either an ERCD or VBAC.
And good news, there’s no paywall so access is free!
The headline message for the woman is:
…risks such as uterine rupture are higher for women attempting a trial of labor following a previous cesarean delivery than those having an elective repeat cesarean delivery; however, the overall risks are low in both groups.
So how does it break down?
One study was based in the UK and the other in Australia, and both calculated that the uterus ruptures in approximately 2 in 1,000 planned VBAC cases and 1 in 1,000 planned ERCD cases. These figures are lower than those previously reported and communicated to patients, which range from 4-12 ruptures in every 1,000 women planning VBACs. The authors of the Australian study put this down to the hospitals following standardised treatment plans that were designed using the latest evidence. Either way, the results are encouraging.
The British study also found that the risk of rupture is higher for women who have had two or more previous caesarean deliveries, less than 12 months since their last caesarean section, or whose labour was induced (up to roughly 6 in every 1,000 cases, if I’ve calculated correctly, so still relatively low).
As for how the intended modes of delivery played out, nearly 98% of women who planned an ERCD succeeded, but only 57% of those who planned a VBAC did. Almost 25% of women originally planning a VBAC ended up choosing a caesarian delivery, which suggests they either changed their minds or doctors advised that a caesarian should be carried out instead.
The Australian study also assessed the outcomes for the babies. The researchers recorded fewer serious problems for the babies in the ERCD group when compared with the babies in the VBAC group – approximately 1 in a 100 ERCD births had difficulties, whereas over 2 in a 100 VBAC births had problems for the baby. Serious problems that needed treatment included physical birth injuries, infection and low oxygen in the umbilical cord.
There were two stillbirths in the VBAC group, but as Catherine Spong explains in the summary piece, there’s an important caveat to note. Elective caesarians, by their nature of being chosen, happen at a set time – in the Australian study the C-sections were performed, on average, after 38.8 weeks of term. Laboured vaginal births, by their nature of being involuntary, cannot be booked in, and the average time that these took place was at 40 weeks of term. As a result, it is uncertain whether these stillbirths were associated with the type of delivery or the extra time in the womb (or, even, that they happened by chance – 2 is a very low number from which to draw conclusions).
The state of play
Uterine rupture can increase the risk of stillbirth. According to statistics cited in Spong’s article from the National Institutes of Health in the US, infant death occurs in 6% of cases of a ruptured uterus – given the rates of rupture reported by these two studies, it puts the estimated risk somewhere in the region of 3 deaths every 50,000 ERCDs and 6 deaths every 50,000 VBACs.
Uterine rupture can also increase the risk of brain damage to the baby due to a lack of oxygen (‘hypoxic-ischaemic encephalopathy’, or HIE). Another review estimated this risk to be one in every 1,250 VBACs against practically zero risk in ERCDs.
However, these ever-so-slightly higher risks of complications in VBACs need to balanced against other potential problems associated with caesarian deliveries. Serious infant respiratory problems are more common in elective caesarians (observed to be 3-6 in 400) compared with vaginal deliveries (observed to be 1 in 400). Newborns are also more likely to be admitted to the neonatal intensive care unit (NICU) due to the need for ventilation therapy and more likely to spend longer than seven days in hospital. Other caesarian-specific risks to the mother, such as dislodged blood clots, need for a blood transfusion, extended wound healing, a longer stay in hospital and future pregnancy complications, are also present.
The extent of some of these risks is greatest in the cases of caesarian sections following failed VBACs, which means understanding which women are most likely to have a successful VBAC is hugely important. A group of US clinicians highlighted various factors that increase the likelihood of a successful VBAC: women with one previous caesarian delivery with a low transverse incision, women who at some point have had a prior successful vaginal delivery, and women who had their caesarian because the baby presented breech or some other form of malpresentation rather than for other reasons. Vaginal births in general are more successful when women have access to high level of healthcare, something we should always seek to protect and improve wherever necessary.
Other factors decrease the likelihood of a successful VBAC: failure of the labour to progress or baby to descend during a previous TOLAC, a higher age and weight of the mother, and preexisting medical conditions such as hypertension or diabetes.
What does all this population data mean for the individual woman? The risks for TOLAC seem reasonable in the context of the inherently uncertain process of labour, but women should be properly prepared and counselled to understand the benefits and risks. This should ideally be done with full reference to real numbers and so that the discussion takes the individual’s status into account. That way, the chances of a satisfactory outcome for mother, child and doctor can be at its greatest.