Trends in induction of labour

How are trends in induction of labour changing? And has the publication of the controversial ARRIVE Trial affected this?

Two recent studies have added to our knowledge about the effects of changing guidelines and narratives on trends in induction of labour. This is vital research, as it shows how induction directly impacts experiences and outcomes for women, babies and families.

The first study was published in the American Journal of Obstetrics and Gynecology. It was, “a population based, retrospective cohort study of low-risk nulliparous women who initiated prenatal care by 12 weeks gestation with singleton, non-anomalous pregnancies that delivered at ≥ 39 weeks” (Gilroy et al 2022).

In other words, these are healthy women. They should, on the whole, be able to expect to give birth without the need for too much intervention. As long as they have caregivers and an environment which supports this, of course.

 

Before and after ARRIVE

The researchers set out to look at changes in obstetric practices and pregnancy outcomes following the ARRIVE trial. To do this, Gilroy et al (2022) looked at practice before and after the trial was published (while ignoring the year around publication, to enable any changes to be more visible) and considered data from more than two and a half million births.

Their findings are fascinating.

After the ARRIVE Trial was published, women were more likely to undergo induction of labour. They were also more likely to receive a blood transfusion, and be admitted to a maternal intensive care facility. Their babies were more likely to need assisted ventilation at birth and more likely to have a low APGAR score at 5 minutes.

 

Women who gave birth after the ARRIVE Trial had what the authors described as “a significantly lower rate of caesarean delivery” (Gilroy et al 2022). However the absolute difference in caesarean rates is very small: 27.9% of women had a caesarean before the ARRIVE Trial was published and 27.3% of women had a caesarean afterwards.

It is important to remember that these are healthy women without risk factors. So those caesarean rates are high both before and after publication of the trial.

 

A critical commentary

Other obstetric researchers have commented on this study. In a letter to the American Journal of Obstetrics and Gynecology, Vouga & Desseauve (2022) write that:

“Congruently, Gilroy et al. observed an increased induction rate after the ARRIVE trial (36.1% versus 30.2%; aOR=1.36 (1.36-1.37)) and a reduced CS rate (27.3 % 36 versus 27.9%; aOR=0.94 (0.93-0.94)). Although significant, this reduction in the CS rate (0.6%) was way below the expected 4%, observed in the experimental conditions of the ARRIVE trial.”

They highlighted the poorer outcomes in the induction group, as I discussed above, and asked whether,

“…one might question whether a 0.6% reduction in the CS rate really justifies a change in obstetric practices? In large cohort studies, statistical significance is often achieved, but might not always reflect clinical relevance. Furthermore, in both the ARRIVE trial and Gilroy et al.’s work, the rate of CS for low risk nulliparous women was higher (i.e. 18.6% / 22.2% and 27.3% /27.9%, respectively) than what has been reported in other countries, such as the United Kingdom, where the risk of emergency CS among low risk nulliparous women was estimated to range around 12.2 to 12.9%.

In settings with a lower rate of CS, such a small reduction in the number of CS might even be less significant and further questions changing obstetric practices.” (Vouga & Desseauve 2022)

 

And in Australia?

Another team of researchers in Australia begin by noting that, “The World Health Organisation recommends that induction of labour (IOL) be performed only with a clear medical indication.” (O’Sullivan et al 2022).

Their research analysed trends in induction of labour in a large Australian metropolitan maternity service between 2015 and 2020. They also focused on healthy women with single babies, and they looked at the reasons why labour was induced as well as the rate of induction. Their findings were just as interesting and just as worrying as those of Gilroy et al (2022).

O’Sullivan et al (2022) found that, of about 46 530 livebirths occurred during the study period, labour was induced in 31.7%.

“The proportion of women undergoing IOL increased from 29.8% in 2015 to 33.4% in 2019 (P < 0.001). The proportion of inductions for DFM [decreased fetal movements] and elective indications increased over time, with a substantial decrease in ‘post-dates’ IOL.” (O’Sullivan et al 2022).

The researchers conclude that, “This large contemporary analysis of IOL trends in Australia has demonstrated rising rates and changing indications for IOL. There remain large knowledge gaps in areas such as care of women with DFM, definitions and management of ‘post-term pregnancy’, and the economic and service impacts of rising trends in the rate of IOL.” (O’Sullivan et al 2022

 

What has changed?

A closer look at the Australian data show us what has been changing, and this reflects the experiences of many midwives and doctors. Some of the things that I commonly hear from clinicians in the UK, Australia and elsewhere when they discuss trends in induction include that:

  • “There seem to be more inductions for reduced fetal movements despite a lack of evidence that this is beneficial.”
  • “Post-term is a less common reason for induction now because more and more women get told they need induction for another reason before then even get to that point in pregnancy.”
  • There has been an increase in induction for gestational diabetes, again despite a lack of evidence of benefit.

All of these things were confirmed in the Australian study.

“The proportion of IOL for DFM and elective reasons increased from 2.6 to 10.8% and 17.4 to 21.8%, respectively. Post-dates subcategories reduced over the study period from a total of 25.3 to 15.4% (Fig. 2). The most common indications for IOL over the entire study period were (in order of frequency) maternal diabetes, gestational age ≥k41 + 0, social/elective reasons, DFM and maternal hypertension.” (O’Sullivan et al 2022)

 

Why this matters

As many readers of this newsletter will know, I spent a large proportion of late 2021 focusing on induction of labour as I wrote In Your Own Time (Wickham 2021). Data from studies like these two (and I am certain that there will be more) evidence how much we need to keep studying, writing and talking about these issues.

Induction of labour has significant consequences, downsides and knock-on effects as well as potential benefits. It’s vital that anyone being offered induction is also offered clear, evidence-based information, explanation of the limitations of current research AND discussion of the wider issues so they can make the decisions that are right for them.

 

If you’d like to explore these ideas further, I have written more about this in In Your Own Time: how western medicine controls the start of labour and why this needs to stop
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Gilroy LC, Al-Kouatly HB, Minkoff HL et al (2022). Changes in obstetric practices and pregnancy outcomes following the ARRIVE trial. AJOG https://doi.org/10.1016/j.ajog.2022.02.003

O’Sullivan C, Wilson E & Beckmann M (2022). Five-year trends in induction of labour in a large Australian metropolitan maternity service. ANZJOG https://doi.org/10.1111/ajo.13486

Wickham, S (2021). In Your Own Time: how western medicine controls the start of labour and why this needs to stop. Avebury: Birthmoon Creations.