rmc28: (uterus)
Rachel Coleman ([personal profile] rmc28) wrote2012-01-28 12:20 pm
Entry tags:

VBAC research

I have done lots of reading about VBAC (vaginal birth after c-section) and ERCS (elective repeat c-section). It might have made a more productive meeting with the obstetrician on Monday if I'd done it first. I've primarily used the following resources:

Home Birth Reference Site (HBRS)
Guidelines from the Royal College of Obstetricians and Gynacologists on Birth After Previous Caesarean Birth (Green-top 45) (PDF downloadable from that link). (RCOG)

I very much like this sentence from the RCOG guidelines:

There are no randomised controlled trials comparing planned VBAC with planned ERCS and this may be an unrealistic aspiration.

On the specific facts and statistics asserted by the obstetrician:

1. The risk of uterine rupture is 1 in 200:
HBRC says "less than 1 in 200" but also note that 10-15% of mothers planning home births transfer to hospital for all reasons, and in the only (small) study that looked at planned home VBACs, 28% of women transferred for all reasons.
RCOG (p5, section 6.3) give the uterine rupture risk is 22-74/10,000 (1 in 500 to 1 in 135). There is "virtually no risk" of uterine rupture with ERCS.

2. The c-section means I am not low risk:
HBRC has a quote it would have been good for me to have read beforehand:
However much we support women who want home VBACs, even the most radical childbirth activist must acknowledge that a woman with a past caesarean is not low-risk. She has the known additional risk factor of uterine rupture, and this makes her medium-risk or high-risk in the eyes of most medical practitioners.

RCOG (p5, section 6.3) say
Although a rare outcome, uterine rupture is associated with significant maternal and perinatal morbidity and perinatal mortality ... maternal death from uterine rupture in planned VBAC occurs in less than 1/100,000 cases in the developed world
Also planned 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.

This latter statistic is what someone medical (midwife?, obs?) told me shortly after Charles's birth: that I could 'definitely' deliver normally next time and the risk would be the same as for the first-time mother. They meant just the narrow "risk of the baby dying" and not the wider range of risks to both mother and baby (increased morbidity), but I didn't know that, so it lodged in my head as "VBAC is as safe as first-time birth", which is wrong.

3. The risk of uterine rupture means that I "must" have constant monitoring of the fetal heart rate while in active labour, because I will need a "crash" c-section to save both me and the baby if it happens.
True uterine rupture is symptomatic, which means that the mother is losing enough blood for her and the baby to be affected. Her blood pressure falls, her pulse changes, she may experience abnormal pain in one area, even through an epidural. The baby goes into distress as its oxygen supply is interrupted. This situation is extremely dangerous for the baby and for the mother, and the baby must be delivered urgently by caesarean if it is to live.
and also
The first warning signs of uterine rupture are usually changes in the baby's heart rate.

But add two pieces of context:

1. It's no good having constant fetal monitoring if no-one is paying attention or if the heart rate changes are ignored. There are links from that page, which I have not followed, describing cases in the UK in recent years where this happened, and people died.
2. The chances of needing a crash c-section for any reason (e.g. fetal distress, cord prolapse, or hemorrage) is about 5 times higher than that for uterine rupture alone.

RCOG (p9, section 8) recommend
planned VBAC should be conducted in a suitably staffed and equipped delivery suite, with continuous intrapartum care and monitoring and available resources for immediate caesarean section and advanced neonatal resuscitation

Women should be advised to have continuous electronic fetal monitoring following the onset of uterine contractions for the duration of planned VBAC

The relative and absolute risks of severe adverse events in the absence of continuous electronic fetal monitoring are unknown.

Continuous intrapartum care is necessary to enable prompt identification and management of uterine scar rupture.

The last bit goes on to describe a number of symptoms that might indicate scar rupture, as well as changes in the fetal heart rate, that an observant midwife or obstetrician could detect.

Other useful information on risks.

Induction or augmentation for VBAC is a very bad idea:
RCOG (p10, section 9):
[there is a] two- to three-fold increased risk of uterine rupture and around 1.5-fold increased risk of caesarean section in induced and/or augmented labours compared with spontaneous labours.
Induction of labour using oxytocin (pitocin, syntocinon) and prostaglandins (eg prostaglandin gel, prostin) have been associated with increased risk of uterine rupture. Misoprostol (Cytotec) has been associated with a greatly increased risk of rupture.

Instrumental delivery raises risk of uterine rupture according to HBRC (it is not mentioned in the RCOG guidelines)

Morbidity statistics comparing VBAC to ERCS are complicated
From HBRC:
Successful VBAC has approximately one-fifth of the morbidity of ERCS
Unsuccessful VBAC (i.e. ending in an unplanned c-section) has about twice the morbidity of ERCS
Approximately 80% of VBACs are successful, so overall VBAC has lower morbidity than ERCS

RCOG (p3, section 6.1) put the chances of successful VBAC at 72-76%. The best predictor of a successful VBAC is a previous successful vaginal birth. The main risk factors for a failed VBAC are:
  • induced labour
  • no previous vaginal birth
  • body mass index greater than 30
  • previous caesarean section for dystocia
When all the above are present, the chances of successful VBAC are only 40%. I note that I have two of the four. Other relevant risk factors are: VBAC at or after 41 weeks of gestation, birth weight greater than 4000 g; no epidural anaesthesia, previous preterm caesarean birth, cervical dilatation at admission less than 4 cm, less than 2 years from previous caesarean birth, advanced maternal age, non-white ethnicity,
short stature and a male infant.

Respiratory problems in the fetus:
RCOG (p6-7, section 6.3) give a lowered risk of respiratory problems with VBAC (2-3% vs 3-4% with ERCS). Delaying ERCS to 39 weeks gives a 5/100 reduction in risk of respiratory problems, with a 5/10,000 increase in the risk of stillbirth.

ERCS increases the risk of serious complications in future pregnancies
I don't want any more pregnancies, so this is less of a concern for me.
naath: (Default)

[personal profile] naath 2012-01-30 10:40 am (UTC)(link)
Ah, well researched numbers; so much more comforting that consultants staring at you and trying to make you agree to do what they want.

Some of these numbers look scary to me, but of course it's not me that needs to use them to make a choice. Hopefully your doctors can be persuaded that whatever you decide on is your fully informed choice.