In this blog in our Evidence for Everyday Midwifery series, midwife Lisa Smith @kirsten_lisa looks at Cochrane evidence on prelabour rupture of membranes at term and whether it’s better to offer induction or to wait.
Many of the women I meet in our birth planning clinic tell me about their last labour being induced following prelabour rupture of membranes. Most will recount stories of a long process filled with uncertainty and pain. Some may have had prostaglandin to ripen their cervix, others may have been given an oxytocin infusion from the outset. Many will have requested an epidural, a proportion of which may have been delayed due to other clinical priorities for the anaesthetist on duty leaving the woman in pain. Needless to say, they are worried about induction and want to avoid it happening again.
So, if women’s waters break at term, is it better to wait 24 hours before offering induction in order to provide an opportunity for labour to start naturally or is it worth offering early or even immediate induction?
Prelabour rupture of membranes: what next?
Around 8 to 10 per cent experience prelabour rupture of membranes prior to the onset of labour from 37 weeks (NICE 2008). However, depending on which evidence you look at, 60-95 per cent of these women will then go into labour within 24 hours (NICE 2014; Middleton et al 2017).
Because ruptured membranes are associated with a higher risk of neonatal infection than intact membranes, the current national guidance recommends offering induction of labour approximately 24 hours after women’s waters break (NICE 2008, 2014). If a woman declines this option, she can be offered ‘expectant management’ which usually involves recording her temperature regularly at home and reporting to staff any concerns about fetal movements, liquor colour and smell or other symptoms. Until labour commences, it is also recommended that fetal movements and heart rate are assessed every 24 hours (NICE 2014).
Cochrane evidence on prelabour rupture of membranes
This updated Cochrane review revisits whether it is better to offer either ‘planned early birth’ (i.e. immediate or early induction within 12 hours of rupture of membranes) or to wait at least 24 hours, which is referred to here as ‘expectant management’. The review compares expectant management with intravenous oxytocin infusion, prostaglandin E2, various forms of misoprostol as well as acupuncture and Caulophyllum – a homeopathic preparation which I had to Google.
The review found that planned early birth reduced the relative risk of maternal infectious morbidity by around 50 per cent compared to the expectant management group. For babies, planned early birth also reduced the relative risk of definite or probable early-onset neonatal sepsis by around 25 per cent compared to those with mothers in the expectant management group. Furthermore, the babies were less likely to be admitted to the neonatal unit or to require antibiotics. Hospital stay for mums and babies was also shorter in the planned early birth group, and women were more likely to be satisfied with their experience.
No difference in risk was seen in the likelihood of caesarean section – even when a subgroup analysis by parity was performed, instrumental birth, epidural use, serious maternal morbidity or mortality, Apgar score, definite early-onset neonatal sepsis or perinatal mortality amongst others.
Let’s talk about risk*
Before we go any further, let’s just think about risk here. While the relative risk reductions seem large – the absolute or actual risk to women is much smaller. So, for instance, 207 women out of 3442 cases in the planned early birth group versus 377 women out of 3442 cases in the expectant management group developed some kind of infectious morbidity. That’s about 6 per cent and 11 per cent respectively – representing an absolute risk reduction of 5 per cent in the planned early birth group which sounds less dramatic than the relative risk reduction of 50 per cent. Similarly, 110 babies out of 3677 cases in the planned early birth group versus 149 babies out of 3637 cases developed definite or probable early-onset neonatal sepsis. That’s an absolute risk of nearly 3 per cent in the early planned birth group compared to 4 per cent in the expectant management – a 1 per cent difference in actual risk.
It’s not clear-cut…
On reading the plain language summary it seems a no brainer to offer women planned early birth rather than ‘expectant management’ with induction from 24 hours post rupture of membranes. But then you start to wonder how sensible and achievable this would be when the majority of women will go into labour within 24 hours anyway. And once you get into the detail of the included studies, other problems become apparent.
For me, the big issue is that the studies in the expectant management group included not only women induced 24 hours after their waters broke, but also women left for 48, 72, 96 hours, or until they went into spontaneous labour, unless sepsis was suspected in the meantime. Twenty three trials were included overall, the largest of which involved 5042 women. This study, by Hannah et al (1996), compared immediate induction with intravenous oxytocin or vaginal prostaglandin E2 gel versus expectant management for 96 hours. In contrast, there were 14 studies involving 2267 women that specifically compared early planned birth with induction at 24 hours.
In my mind, such a mixed bag in the expectant management group makes it difficult to say for sure whether we should give women a stronger recommendation for earlier induction than the current national recommendation of 24 hours.
More reasons for caution
There are other reasons to be cautious about the findings, blinding of participants and staff being one. While some of the trials were able to successfully use KY jelly instead of prostaglandin gel, it’s rather more challenging to apply the same principle to an intravenous oxytocin drip, which is usually associated with a suite of active management interventions.
Studies also used different definitions for outcomes such as chorioamnionitis and suspected or probably neonatal infection. For instance, Hannah defines chorioamnionitis as ‘fever before or during labour was defined as a temperature 37.5°C on two occasions 1 hour apart or a temperature of 38°C. Other signs of chorioamnionitis were a maternal white-cell count 20,000 per cubic millimetre or foul smelling amniotic fluid’ while other studies used histological evidence of placental inflammation or evidence of invasion of the amniotic cavity by microorganisms. Similarly, for neonatal sepsis some authors used positive blood cultures, while others used clinical signs and symptoms and treatment with antibiotics. In those cases, we know the blood culture will often come back negative.
The inclusion and exclusion criteria also appeared to differ between the included trials and this is also a key issue when assessing reliability and generalisability. For instance, few of the trials were explicit about the inclusion of women with Group B Streptococcus (GBS) colonisation or how they were managed.
The current UK recommendation, currently under review, is to offer immediate induction to women colonised with GBS who experience spontaneous rupture of membranes at term to reduce the risk of early-onset neonatal GBS disease (RCOG 2012).
These issues undermine the reliability and generalisability of the findings of this review somewhat and how we apply it to everyday practice. Indeed the authors of the review acknowledge the low quality of evidence and the potential sources of bias.
Where does this leave us?
So where does this leave us, particularly in the context of a national drive for ‘airline levels of safety’ within maternity care and public concerns about poor outcomes in childbirth (NHS England 2016; Campbell 2017).
As with any intervention, it’s important to discuss the pros and cons of induction of labour with women when their waters break to enable them to make an informed choice about whether they choose planned early birth, induction around 24 hours later or even a longer period of expectant management.
The absence of stronger evidence in this review suggests the recommendation of induction at 24 hours, in the absence of other risk factors, is likely to remain the most practicable approach since the majority of women are likely to go into labour before this time.
Lisa Smith has nothing to disclose. Views expressed are Lisa’s own.
References may be found here.
* Editors note: for more on risk, check out this blog from understandinguncertainty.org