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The ARRIVE trial. A breakdown.

The ARRIVE Trial (A Randomised Trial of Induction Versus Expectant Management).

So you may have heard about this recent trial concerning Induction of Labour. There has been a lot of discussion about it amongst birth workers and the repercussions of the findings. So here is the watered down version with some advice on how to interpret the findings in your practice or pregnancy.

Why did they do the trial?

The trial was conducted to identify if elective induction of labour (IOL) with NO MEDICAL REASON @39 weeks gestations would result in fewer neonatal complications and mortalities compared to waiting at least 40 weeks and 5 days for IOL if labour had not started already.

The researchers also wanted to identify if elective induction at 39 weeks had an effect on the risk of caesarean section.

What did they do?

This was a US based study. The study happened across 41 hospitals all over the country.

The trial had specific inclusion criteria:

- It was for first time mothers (Primips)

- Single pregnancy

- Cephalic presesntation (Baby had to be head down)

- No major medical conditions

50,000 women were screened. Of these 22,533 were found to be eligible for the study. And of this number 6106 women agreed to take part.

From this total the women were split up:

- 3062 women were allocated to the IOL @39 weeks group

- 3044 women were allocated in to the Expectant Management group (to await natural labour or for IOL at 40+5 weeks)

What were the results?

IOL @ 39 weeks DID NOT IMPROVE primary outcomes when it comes to complications or mortality of neonates. So IOL at 39 weeks made no difference to newborn conditions in this study.

For mothers the IOL @ 39 weeks was linked to a lower rate of Caesarean Section. 19% in the IOL group vs 22% in the Expectant Management group.

It was also identified that women in the IOL group had a 9% chance of developing high blood pressure compared to 14% in the Expectant Management group.

So should we induce everyone @ 39 weeks to lower the caesarean section rate?


This study has given some food for thought sure. It is good for us to reference this when making informed decisions regarding care. But remember That all studies have their flaws. And NO professional bodies such as ACOG, RCOG etc have changed their guidelines to reflect these findings.

Study Flaws? Points to consider….

- The study is not actually that generalisable. It is applicable to the women matching inclusion criteria but we cannot readily apply it to multips or any women with any pre-existing medical conditions no matter how major or minor.

- It would only be applicable if every IOL was carried out in the same method and over the same time frame as this study.

- It makes sense that the longer pregnancies saw a raise in blood pressure. This can be quite common towards the end of pregnancy. Longer pregnancy generally has the potential for complications to arise.

- Longer pregnancies can also make doctors twitchy. Their ability to control the birth lessens and this can often lead to a knee jerk reaction of caesarean section.

- The researchers in the study gave women 12 hours in early labour before they declared the induction a failure. This is not applicable to real practice. With physician led care women are rarely given this opportunity. There is a tendency to diagnose “failed induction” much sooner.

- Have you heard of “The Hawthorne Effect”? Also known as the observer effect. This is when people’s behavioural response changes when they know they are being watched. So by this I mean most Doctors will be more inclined to push for a normal delivery following IOL at 39 weeks as they know their C/S rates are a measurable outcome. This is not standard thinking in real practice as it is more fiscally and physician schedule led.

- This study is an American one. America has one of the highest rates of maternal and neonatal mortality and morbidity in the developed world. Their model of care is physician led and profit driven. Therefore the findings of this study are not easily applied to midwifery led models of care (i.e the NHS).

Remember there are other evidence based ways to reduce your risk of caesarean section:

- Intermittent Auscultation

- Continuous support from a midwife or doula

- Walking in labour/Active birth

- Staying Hydrated

- Planning a waterbirth.

So yes, the ARRIVE trial gave some points to think about an explore further but do they warrant a change in practice? Nope, they do not! So if your Doctor uses this as a reference point for evidence for elective IOL at 39 weeks just remember that no guidelines have been changed to support the findings and if you feel you need to then seek a second opinion or Midwife/Doula support.

Nikki xx

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