Uterine rupture is rarer than previously thought
Published on Tuesday, 13 March 2012 Tweet
The risk of uterine rupture in pregnancy and labour is very small and lower than previously thought, according to a new UK Obstetric Surveillance System (UKOSS) study.
Most cases of uterine rupture happen in women who've had a caesarean section before.
However, the UKOSS researchers found that the risks remain small even in women planning a normal birth after a previous caesarean – though they are higher than those that opt for another caesarean.
They say that there is no need to change current guidance on birth after a previous caesarean, which is that women should be able to plan the birth they feel most happy with, after discussing the risks and benefits of caesarean and vaginal birth with their doctors and midwives.
'Uterine rupture is a severe but thankfully very rare complication. We found that many of the hospital maternity units across the country don't even see one case a year,' says Professor Marian Knight of the National Perinatal Epidemiology Unit at Oxford University, who led the study.
'Among women who've had a previous caesarean, there is a higher risk for those planning a normal birth rather than another caesarean. But the risk remains very small, occurring in just 0.2% of such pregnancies.'
She adds: 'Given that this figure is lower than many previous estimates, there should be no extra reason to worry. We see no reason to change current advice that women can choose how they would like to have their baby after a previous caesarean, and that in general a vaginal birth should be possible.'
The study is published in the journal PLoS Medicine and was funded by the UK charity Wellbeing of Women and a National Institute for Health Research (NIHR) Programme Grant.
The Oxford researchers found that uterine rupture occurs in just 2 in 10,000 pregnancies in the UK – confirming that this is a rare complication. The vast majority of cases (139 out of 159) were in women who'd had previous caesarean sections.
Uterine rupture is still rare among women who have had a previous caesarean section and plan to have a normal birth at 21 per 10,000 pregnancies. But this is higher than in those who elect for another caesarean section, where the incidence is 3 per 10,000 births.
Professor Knight adds: 'Uterine rupture is not the only complication that should be taken into account when planning births following a previous caesarean delivery. These findings need to be considered alongside other small risks and benefits of either vaginal or caesarean birth. This is why it should be an individual choice for women in consultation with their midwives and doctors.
'While there may be an increase in risk of uterine rupture in planning normal birth after a caesarean, electing to have another caesarean can have other associated risks. C-sections are very safe operations but there are small short-term risks of infection or blood clots, there is the often longer recovery period and there are consequences for subsequent births. For example, the more caesareans you have, the more likely hysterectomy and uterine rupture becomes.'
The researchers compared outcomes for the uterine rupture cases with those for a control group of 448 women giving birth after previously having had a caesarean section.
Other factors that were associated with increased risk of uterine rupture were the number of previous caesarean sections the mother had had; a short time since the previous caesarean delivery; and induction of labour.
Professor Knight explains what can be taken from these findings: 'For women who have had a caesarean section, what may be the most useful thing to know is that you will have a lower risk of uterine rupture if you wait at least 12 months before conceiving again.'
She adds: 'Obstetricians and midwives can now be aware that, although rare, inducing labour, or using oxytocin to strengthen contractions, is associated with greater risk of uterine rupture. We now have a good measure of the size of that risk, enabling this information to be put into perspective when discussing birth options with women.'
For more information please contact Professor Marian Knight on +44 (0)1865 289727 or marian.knight@npeu.ox.ac.uk
Or the University of Oxford press office on +44 (0)1865 280530 or press.office@admin.ox.ac.uk
Notes to Editors
* Uterine or womb rupture, a rare complication where the womb wall tears open, occurs most often in labour when the womb is under pressure and contracting. Although it is rare, it can be very severe and even life-threatening for mother and child.
Most cases of uterine rupture occur in women who've had a caesarean section before, when the old scar tissue splits.
The seriousness of uterine rupture has led some to wonder whether caesarean sections should be used more often for women who've had a caesarean previously.
* Current advice is that women who've had a caesarean should have a choice in planning either a vaginal or caesarean delivery for subsequent births, but that vaginal birth should be possible and is often encouraged.
However, there has been a lack of definitive data on how often uterine rupture occurs in the UK to be absolutely sure of the risks.
Therefore, the Oxford University researchers set out to accurately measure the incidence of womb rupture.
* In order to get a much better measure of the incidence of womb rupture than previous estimates, the researchers used the UK Obstetric Surveillance System (UKOSS) to identify confirmed cases of uterine rupture across the UK between April 2009 and April 2010.
UKOSS is a national research system that allows comprehensive information to be assembled about pregnancy complications and their care. It collects data from all hospitals with obstetrician-led maternity units in the UK, so it is as complete as possible.
* There were 159 cases of uterine rupture in the 13 months between 1 April 2009 and 30 April 2010. In that time there are estimated to have been around 800,000 births in the UK, giving an estimated incidence of uterine rupture of 2 per 10,000 pregnancies.
Two women with uterine rupture died and there were 18 deaths among the babies that were associated with the uterine rupture event.
* The paper 'Uterine rupture by intended mode of delivery in the UK: a national case-control study' by Kate Fitzpatrick and colleagues is to be published in PLoS Medicine with an embargo of 21:00 UK time / 17:00 US Eastern time on Tuesday 13 March 2012.
* The study was funded by the UK charity Wellbeing of Women and a National Institute of Health Research (NIHR) Programme Grant.
* The National Perinatal Epidemiology Unit (NPEU) is a research unit at Oxford University. Established at the University of Oxford in 1978, the mission of the NPEU is to produce methodological rigorous research evidence to improve the care provided to women and their families during pregnancy, childbirth, the newborn period and early childhood as well as promoting the effective use of resources by perinatal health services. The unit has more than 80 staff including epidemiologists, public health physicians, midwives, nurses, paediatricians, social scientists, and information specialists.
* The National Institute of Health Research (NIHR) provides the framework through which the research staff and research infrastructure of the NHS in England is positioned, maintained and managed as a national research facility. The NIHR provides the NHS with the support and infrastructure it needs to conduct first-class research funded by the Government and its partners alongside high-quality patient care, education and training. Its aim is to support outstanding individuals (both leaders and collaborators), working in world-class facilities (both NHS and university), conducting leading-edge research focused on the needs of patients. www.nihr.ac.uk
* Programme Grants for Applied Research are awards made by the National Institute for Health Research (NIHR) to fund high quality research that address areas of priority or need for the NHS. Programme Grants award up to £2 million over three to five years to the best applied research teams from the NHS and academia working together to provide evidence to improve health outcomes in England through the promotion of health, the prevention of ill health and optimal disease management (including safety and quality). Programme Grants typically fund programmes of interrelated, high-quality research projects and associated infrastructure that are designed to deliver findings that can be directly and practically applied in the relatively near future, for the benefit of patients and the NHS. www.pgfar.nihr.ac.uk
* Oxford University's Medical Sciences Division is one of the largest biomedical research centres in Europe, with over 2,500 people involved in research and more than 2,800 students. The University is rated the best in the world for medicine, and it is home to the UK's top-ranked medical school.
From the genetic and molecular basis of disease to the latest advances in neuroscience, Oxford is at the forefront of medical research. It has one of the largest clinical trial portfolios in the UK and great expertise in taking discoveries from the lab into the clinic. Partnerships with the local NHS Trusts enable patients to benefit from close links between medical research and healthcare delivery.
A great strength of Oxford medicine is its long-standing network of clinical research units in Asia and Africa, enabling world-leading research on the most pressing global health challenges such as malaria, TB, HIV/AIDS and flu. Oxford is also renowned for its large-scale studies which examine the role of factors such as smoking, alcohol and diet on cancer, heart disease and other conditions.
