Full term is actually considered 39-41 weeks pregnant, and an induction (artificially starting labour) because you are close to your due date is technically considered elective, meaning there’s no medical indication.
Today I’m going to spend some time talking about the ARRIVE trial, as it’s a big driver behind this new movement to induce before 41 weeks (when mom’s are typically induced based on due date and not other medical reasons).
What is the ARRIVE study?
“A Randomized tRial of Induction Versus Expectant management” was released in 2018 in the New England Journal of Medicine (a Massachusetts journal).
Their official abstract is as follows:
So looking at that journal abstract, what do we see?
- This study looked at low-risk, first-time moms.
- It compared induction in the 39th week of pregnancy with expectant management.
- Primary outcome they were looking at: risk of baby dying or having severe complications.
- Secondary outcome: risk of Caesarean.
- Study included 6100 women total; half in induction group, half in expectant management.
Rates of babies dying or having major complications was similar between the groups, but when induced at 39 weeks, the rate of Caesarean was significantly lower (18.6% versus 22.2% in expectant management group).*
So this study, my friends, has really impacted pregnancy care and induction recommendations.
If we stop here, we would probably all nod our heads, not blinking an eye when our provider recommends early induction, right? I think most of us would like to reduce our risks of Caesarean Section?
What if I told you that digging into the data reveals a lot of other REALLY important factors to consider when confronted with the recommendation of an early induction?
Let’s get digging.
Who was eligible for the study?
This trial only looked at first -time moms.
If you have already had one baby, this trial is not applicable to you and thus the recommendation to induce at 39 weeks to reduce your risk of CS is not evidence-based.
Who signed up for this study?
Those who agreed to be in the study were those who were fine being assigned to an early induction group, meaning that those who might want to avoid early induction may not have opted to sign up! The original group of eligible women was 22,000, but only 6000 signed up in the end. This study potentially captured a segment of the population whose preferences don’t include low intervention birth.
What was the control group?
They stated that the early induction group was compared to an “expectant management” group, but it is VERY significant to know that they were not comparing early induction to spontaneous labour! The expectant management group was all induced at 40+4 at the latest if they were still pregnant! Most first-time moms will be pregnant longer than 41 weeks, and the trial outcomes do not take into account spontaneous labour data after 40+4 weeks. That is INCREDIBLY significant.
Now that I’ve enlightened you, I’m going to start putting quotations marks around “expectant management”, because it’s not actually expectant at all. The term “expectant” is usually used to describe a normal, physiological progression without intervention.
What if someone in the “expectant management” group wanted to change their mind?
Women in the ”expectant management” group could change their minds at any point. This means that there could have been even fewer rates of spontaneous labour than you would expect from a group of first-time moms pregnant past 39 weeks.
What kinds of induction protocols were they using?
The induction protocols included longer wait times for labour to start leading to lower rates of “failed induction”, because these researchers and providers wanted their inductions to work and result in a vaginal delivery! If the outcome is looking at the effects of early induction on CS rates, they will be inclined to take their time.
What does this all mean for me?
A 39 week induction should be offered to low-risk moms, when it is in-line with your values, staffing levels are good, and protocols for failed inductions don’t lead right to CS. The hospital has to be able to accommodate multiple moms on days-long inductions for you to benefit from the 3% reduced CS risk.
If you live in a community with high CS rates, especially when it comes to “failed inductions”, this data is not generalizable to you.
Take home lesson:
You should not be pressured into, nor denied, an elective induction at 39 weeks.
But I’m not done yet.
If your goal is to reduce your risk of Caesarean Section, this is not the best way to do it. There are much more cost effective and less interfering ways to reduce the risks of an operative birth:
1) Ambulation: a 1997 study of low-risk women showed a 50% less risk of CS when women spent a significant amount of time walking and moving around in labour.
2) Using Intermittent Auscultation: as stated in my previous blog post “Fetal Monitoring In Labour“, continuous Electronic Fetal Monitoring use in labour is 63% more likely to result in CS instead of intermittent auscultation.
3) Doula care: there is a 39% reduced risk of CS when you hire a doula to help advocate and support you in labour.
🤷♀️ So you tell me: if their goal was REALLY to reduce your Caesarean risk, is this how they should be doing it? 🤷♀️
* This study also demonstrated lower rates of hypertensive disorders in the induction group (5% less), which makes logical sense: first-time moms are at higher risk of hypertension issues at the end of pregnancy, so when you shorten pregnancies for them, you’ll see less high blood pressure. This is not in-and-of-itself reason to induce all first-time moms at 39 weeks.
Albers, L.L., Anderson, D., Cragin, L., Daniels, S.M., Hunter, C., Sedler, K.D., Teaf, D. “The relationship of ambulation in labor to operative delivery”. Jan-Feb 1997. J Nurse Midwifery. Issue 42(1):4-8. doi: 10.1016/s0091-2182(96)00100-0. PMID: 9037929. Accessed online 18 March 2021.
Dekker, R. “The ARRIVE trial”. 5 November 2013. Evidence Based Birth. Accessed online 5 April 2021.
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