Tuesday October 25 2011
The two induction methods had similar outcomes
According to the Daily Mail, a method of inducing labour that dates back to the 1930s “has been found to work as well as modern treatments but with fewer side effects”.
The news is based on a large Dutch trial that examined inducing labour using of a simple mechanical device, called a Foley catheter. Researchers tested the device against the use of hormone gels designed to trigger contractions. The study, which featured 824 women, found that both techniques led to similar rates of spontaneous vaginal deliveries, instrumental deliveries (such as using forceps) and women requiring a caesarean section.
The Foley catheter also seemed to lead to fewer side effects in the women and their babies, although using the method of induction in the first 24 hours led to longer labours. It is unclear which method women would prefer to be offered, as patient satisfaction was not assessed in this study.
Current guidelines from the National Institute for Health and Clinical Excellence (NICE) recommend the use of hormone gels for induction of labour, but not the routine use of mechanical devices for induction. This is because there was limited evidence for their use when the guidelines were written. This new, relatively large trial has shown no important differences between the two methods used in these women. It is possible that the mechanical technique might find a place for women where there may be risks from using hormone gel. The safety and effectiveness of the technique could be reassessed in the light of this new evidence to see whether the guidelines should be amended.
Where did the story come from?
The study was carried out by researchers from various hospitals in the Netherlands and received no external funding. The study was published in the peer-reviewed medical journal The Lancet.
The Daily Mail covered this research well.
What kind of research was this?
The researchers say that a high proportion of induced labours are performed because a woman’s cervix is not ready for the birth and does not open appropriately.
This randomised controlled trial compared two methods for inducing birth in women who had single babies and a reason to be induced. The women were either induced using mechanical means (a Foley catheter) or with application of a hormone gel into the vagina. A Foley catheter is a mechanical device that helps open the cervix. A fluid-filled balloon is inflated in the cervix, which stretches it until it is at an appropriate size to allow birth. The prostaglandin hormone gel mimics the natural mechanism by which a woman’s hormones cause the cervix to open.
The researchers say that hormonal induction has become the method of choice in several countries, but that use of the Foley catheter may result in similar numbers of successful inductions without the need for a caesarean section. They also say that the Foley catheter induction may have several advantages over hormone methods, such as not causing “over-stimulation” of the birthing processes (when hormones cause contractions to be too frequent or too long).
The researchers compared the two methods. They were particularly interested in the rates of caesarean section, but also looked at foetal distress during induction and bleeding after birth.
What did the research involve?
The trial was carried out in twelve hospitals in the Netherlands. The study included 824 women who were over 37 weeks pregnant without twins, who had an “unfavourable cervix”, whose baby was positioned head down and whose waters had not broken. The study did not include women who had already had a caesarean section or who had a condition called placenta praevia, where the placenta is positioned so that it grows over the cervix. Women whose baby had a developmental abnormality or a known hypersensitivity to either method were also excluded.
The women were randomly allocated to either the Foley catheter or the hormone gel groups. They were induced using these methods and, when the cervix was open sufficiently, their waters were broken. In both groups, if the cervix was still unfavourable after 48 hours, the women were assigned a day of rest followed by another 48 hours of induction. If after these five days the cervix was still unfavourable, induction was defined as having failed. Further management was decided on by the obstetrician looking after the women.
The main outcome that the researchers looked at was the rate of caesarean sections. Other outcomes included resorting to instrumental vaginal delivery (for example using forceps), reasons for operative delivery, and time from induction to delivery. The researchers also assessed whether the uterus had been overstimulated, defined as when the women experienced more than 6 contractions within 10 minutes for more than two 10-minute periods, or when they had a contraction lasting more than 3 minutes where the baby’s heart rate changed. Researchers also looked at rates of damage to the uterus, the use of painkillers and antibiotics, infection and whether the women had a haemorrhage in the 24 hours after delivery. Finally, they assessed the health of the baby and recorded any cases where the baby had picked up an infection.
What were the basic results?
The researchers found that the caesarean section rates were much the same between the two groups: 23% of women who had been induced using a Foley catheter required a caesarean section compared to 20% of the women induced using the hormone gel (relative risk [RR] 1.13, 95% confidence interval [CI] 0.87 to 1.47). Likewise, a similar number of women in each group needed extra mechanical help with the birth, such as the use of forceps (11% in the Foley catheter group and 13% in the hormone gel group).
A greater number of women induced with the Foley catheter required a caesarean because they failed to progress in the first stage of birth (12%) than the hormone gel group (8%) (RR 1.63, 95% CI 1.07 to 2.50). The first stage of labour is when contractions cause the neck of the uterus to open. Similar proportions of each group had a caesarean section because their baby was becoming distressed (7% in the Foley catheter group compared to 9% in the hormone gel group).
A similar number of women in each group had assisted deliveries because their babies were distressed. Fewer women in the prostaglandin hormone group (59%) needed an additional hormone called oxytocin to stimulate uterus contractions than in the Foley catheter group (86%). The time from the start of induction to birth was on average 29 hours (range 15-35 hours) in the Foley catheter group and 18 hours (range 12-33 hours) in the hormone gel group.
The groups did not differ in terms of painkillers taken, haemorrhage, overstimulation or health status of the baby. Fewer babies delivered with the Foley catheter (12%) needed to be admitted to the general ward (not an intensive care ward) than those induced using hormones (20%). More women treated with the hormone gel (3%) had suspected infections during birth compared to those induced with Foley catheter (1%).
Overall, there was no difference in the number of adverse events in each group.
How did the researchers interpret the results?
The researchers said similar rates of vaginal delivery and caesarean section occurred when using the Foley catheter and the hormone gel for induction of labour in women who needed it. However, use of the Foley catheter led to fewer maternal and newborn side effects. They say that health professionals should consider a Foley catheter for induction of labour in women with an unfavourable cervix at full term of pregnancy.
This large randomised controlled trial showed no difference in caesarean or vaginal delivery rates after women were induced with either a Foley catheter or hormone gel. The Foley catheter seemed to be associated with fewer maternal and newborn side effects, although not all these associations were statistically significant. The researchers point out that one benefit of the method is that it reduces the need to monitor contractions as closely as with hormonal induction, which carries the risk of overstimulation. They also say that because of the low cost and easy storage of the Foley catheter, its use could be suitable in developing countries.
However, labour lasted longer after induction with the Foley catheter and it is unclear whether this would affect women’s preference for either induction method. The researchers said that a limitation of the study was that they did not assess their patients’ satisfaction with the treatments. Another limitation is that the study did not assess whether this longer birth period would be more costly or use up more staff time. These unexplored factors could be important in deciding which method is more appropriate for a particular birth. Since the treatments appear equally effective, further research into these important areas might help clinicians choose between the two methods.
In the UK, NICE recommends that women with uncomplicated pregnancies should usually be offered induction of labour between 41 and 42 weeks of pregnancy to avoid the risks of prolonged pregnancy. There are other reasons to induce labour and the exact timing should take into account the woman’s preferences and local circumstances. NICE recommends the use of vaginal hormone gels and a pessary, but not the routine use of mechanical procedures. When the NICE guidelines were written (2008), they suggested that there should be further research into the use of mechanical methods in situations where hormone methods carried risks. The guidelines state that there had been a large number of studies, but that these were small and had used different methods, so they did not provide suitable evidence to support the recommendation of mechanical procedures.
This relatively large trial contributes to the available evidence, and is likely to be considered when labour induction guidelines are reviewed in the future.