Women who need help starting labour could have a more comfortable, relaxed birthing experience with the aid of a
specialised balloon.
An Aotearoa New Zealand study seeking pregnant women aims to confirm the safety and effectiveness of the balloon
procedure for induction.
About one in four pregnant women (24 per cent of births) in this country are induced – helped along by labour-inducing
hormones and physical means.
The University of Auckland-led study, called the OBLIGE trial (Outpatient Balloon vs Inpatient Gel), is running in 10
hospitals and looking for more than 1500 women over the next one to two years. It will compare two common methods of
induction: a prostaglandin hormone preparation, and a balloon catheter fed through the cervix (neck of the uterus) - a
thin tube with a small balloon at one end which gently stretches the cervix.
“We’re interested to find out which method is more likely to lead to vaginal birth, be more cost-effective, and which
method New Zealand women prefer,” says study lead Dr Michelle Wise, a senior lecturer in obstetrics and gynaecology at
the university’s School of Medicine.
“Induction is always started in hospital. But studies into women who spend part of the time of their induction at home
suggest women feel less worried, get more sleep, and feel more rested when they come into hospital in labour.”
The main practical difference for mothers is that because the hormone preparation can sometimes cause unwanted and
excessive contractions, women who undergo this method need to stay in hospital until the baby is born so that the baby’s
heartbeat can be monitored for signs of distress. Contractions are unlikely with the balloon method, which means mothers
are usually allowed to go home while the balloon softens and stretches the cervix, usually for about 18-24 hours.
Dr Wise says international research, summarised in a recent Cochrane review, has shown that compared to using
prostaglandin hormone, using a balloon results in less overstimulation of the uterus – which can cause distress in the
baby and trigger an emergency caesarean – and fewer births using instruments such as forceps. No difference emerged in
the time from start of induction to birth or in rate of caesareans. In one study, the women in the balloon group had
lower pain scores.
“The balloon catheter is a more natural way of starting labour, because it encourages the release of women’s own
hormones to soften the cervix and prepare it for labour,” Dr Wise says.
“And by offering women the choice to go home, it could make women feel the experience is less medicalised, more
comfortable and relaxed. The more choice that women have in labour the better.”
Stephanie Bowler, a secondary school teacher from Ellerslie, and events manager husband Anthony decided that Stephanie
would join the study when she was pregnant with their first baby. The decision to induce was made after she went to
hospital with concerns about her baby’s movements, having passed 40 weeks’ gestation. She was randomly assigned to the
balloon group, and after insertion she was sent home.
“It was a strange sensation – you were aware it’s there – but the really nice part was being able to relax in your own
environment. I was able to lie on the couch the rest of the day and wait.” The balloon worked, and some 12 hours after
it was removed baby Florence, now six weeks old, was born healthy via normal delivery.
“The main appeal of having the balloon inserted is being able to go home – if you had young kids at home that would be
really nice and so much easier.”
The OBLIGE trial is running in the following hospitals: North Shore, Waitakere, Auckland, Waikato, Tauranga, Whakatane,
Hawkes Bay, Taranaki, Hutt Valley, and Wellington. Find out more at the study website www.oblige.auckland.ac.nz or email
oblige.study@auckland.ac.nz
The study has received funding from the Health Research Council, Auckland District Health Board, and the Maurice and
Phyllis Paykel Trust.
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