We get it. You’re very pregnant. You’re past 37 weeks and completely over it.

And now you’re being offered an induction.

Your care provider says induction at 39 weeks is perfectly safe.

In fact, it’s likely your care provider is following recommendations based on the recent data from the ARRIVE trial.

The trial data, released at the recent Society for Maternal-Fetal Medicine conference, suggests inducing labour at 39 weeks in low risk women, rather than waiting for labour to begin spontaneously, might result in fewer maternal complications and c-sections.

Should I Be Induced At 39 Weeks of Pregnancy?

This new information is a complete about-face from the current guidelines, which recommend spontaneous labour in low risk women, because of the benefits for both mothers and babies.

The ARRIVE trial is a large, multi centre trial and has significant potential to affect how birth is managed in the future. The trial is ongoing but it’s already generated heated discussion among health professionals, birth workers and mothers-to-be.

What Did The ARRIVE Trial Find?

The ARRIVE trial is a large randomised controlled trial (RCT), and includes 6,106 women, from 41 hospitals.

An RCT is a study that allocates people at random to be subjects in one of a number of clinical interventions. One of the interventions is the ‘control’ or standard for comparison. This could involve a standard practice, a placebo, or no intervention at all.

So far, the only information we have about the ARRIVE trial is the study abstract.

The researchers randomly allocated low risk first time mothers at 38 weeks to either of these situations:

Induction of labour between 39 weeks and 39 weeks 4 days gestation, or
Expectant management, which means they forgo elective birth (induction) before 40 weeks 5/7 days, but give birth by 42 weeks 2/7 days.

There were 3,062 women in the induction of labour group and 3,044 in the expectant management group. The women were very low risk (any with medical complications were excluded), with an average age of 24, and had to be very interested in labour induction (75% of eligible women refused to take part in the trial).

The results of the trial showed:

The risk of high blood pressure/preeclampsia at the end of pregnancy was halved (9% compared with 14%)
The c-section rate was lower in the induction group (19% compared with 22%)
Perceived labour pain was decreased
The induction group felt more in control over their birth experience
Babies from the induction group required less respiratory support after birth (3% compared with 4%).

So does this trial data prove induction at 39 weeks is the best and safest option for low risk mothers and babies?

What The ARRIVE Trial Doesn’t Tell Us

The ARRIVE trial puts forward the suggestion that induction of labour at 39 weeks of pregnancy might reduce maternal and neonatal complications in low-risk women who are having their first baby.

It’s difficult to understand the study fully, as only the abstract is available, but it has raised some discussion points for many concerned health professionals.

What we don’t know about the ARRIVE trial is:

What cervical ripening or labour induction methods were used? This can have a significant impact on induction outcomes.
What are the differences in the cost of care between the induction group and the expectant management group? Does the induction group cost the health system more?
Why was the expectant management group electively induced at 40 weeks 5 days rather than the standard 41 weeks? These women were given 2 days less time to go into labour spontaneously in the trial than is recommended.
How did the researchers qualify the women in the trial as ‘low risk’? Henci Goer, an obstetric research analyst, comments on this here, and demonstrates why it’s unlikely so many women would develop new preeclampsia or hypertension after being admitted to the trial.
For women in the expectant management group, what testing was used during pregnancy, which might have had the potential to increase the likelihood of induction?
Does the c-section rate of 19% in healthy low risk mothers indicate optimal care? Again, Henci Goer discusses this here, and shows studies of planned out of hospital births have fewer c-sections than the induction of labour group. Most hospitals in the US have much higher rates of c-sections, leading us to consider whether the trial outcomes would remain the same in a real world scenario.

Should We Induce Low Risk Women At 39 Weeks?

The ARRIVE trial suggests there are no benefits in waiting for labour to begin spontaneously before 39 weeks, and induction doesn’t increase the risk of c-section or other complications.

However, there are still too many questions to be answered before we can categorically state induction at 39 weeks, when compared with spontaneous labour, is completely safe and beneficial for mothers and babies.

We know induction of labour upsets the complex hormonal process of birth, which prepares babies for life outside the uterus.

The benefits of undisturbed labour include preparing babies to breathe, temperature regulation, promoting bonding and successful breastfeeding.

You can read more in Natural Birth – 5 Huge Benefits For Babies.

The women in the ARRIVE trial weren’t in situations where the real benefits of undisturbed birth could be observed or comparisons made, which would have given a more accurate assessment of whether elective induction of healthy women at 39 weeks really is the best option.

The California Maternal Quality Care Collaborative (CMQCC) published comments on the ARRIVE trial, and looked at whether the results could be attained in real world situations. In California, c-section rates in first time low risk women following induction average 32% and range as high as 60%.

CMQCC suggests the low c-section rate in the induction group of the ARRIVE trial is due to the use of strict labour guidelines and a strict definition of failed induction across all the hospitals involved in the trial.

In a real world scenario, hospitals and care providers in hospitals take varied approaches to labour induction – particularly in relation to management and duration – before c-section is recommended.

CMQCC states if the trial’s strict labour guidelines and definition of failed labour weren’t adopted by all care providers, the c-section rate would be significantly higher if elective induction at 39 weeks became common.

Until further details of the ARRIVE trial are available, elective induction at 39 weeks isn’t recommended by any leading maternal-infant health organisations, such as The American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine (SMFM), and the American College of Nurse-Midwives (ACNM).

Women who are having a healthy, low risk pregnancy should be supported to wait for labour to begin spontaneously.

If your care provider recommends induction for non-medical reasons, it’s important to use evidence-based research to make an informed decision.

Independent (non-hospital based) birth education classes can help you feel confident and informed about your birth choices, without any institutional bias.

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