41⁺⁰, 41⁺³, or 42⁺⁰?

The recent SWEPIS trial from Sweden (click here) in which no baby died after induction at 41⁺⁰ compared to six deaths among those allocated to induction at 42⁺⁰ provoked some soul searching in Scandinavia.

And last week a group of Danish obstetricians invited me to consider whether they should change the gestation at which they offered induction for women with uncomplicated pregnancy from 41⁺³ (click here for guideline in Danish) to 41⁺⁰, i.e. three days earlier.*

I said, “Yes. Women don’t have to accept the offer, but most will, and the earlier date will prevent baby deaths, without increasing Caesareans. Women’s labour experience will be no worse, and no more painful. It may even be better and less painful.” I cited the ARRIVE (click here) and 35-39 (click here) trials in support of the latter assertions.

As an aside I said that the UK National Institute for Clinical Excellence (NICE) recommends offering induction between 41⁺⁰ and 42⁺⁰ weeks, but that the guideline was under review and I anticipated that the new version would recommend 41⁺⁰. To my surprise the audience told me that NICE already recommended 41⁺⁰.

They were right (click here for the summary and here for the full CG70 guideline. It’s on p24).  It reads:

1.2.1.2 “Women with uncomplicated pregnancies should usually be offered induction of labour between 41⁺⁰ and 42⁺⁰ weeks to avoid the risks of prolonged pregnancy.”

I had read that as offer the induction between 41⁺⁰ and 42⁺⁰ weeks. i.e. an offer to induce as late as 42⁺⁰ was acceptable. But it goes on to say;

“The exact timing should take into account the woman’s preferences and local circumstances.”

This removes any ambiguity. I had misread it. The offer must both be made by 41⁺⁰, and include availability of induction from 41⁺⁰, so that the woman can choose the timing.

Consider a woman whose fetus died at 41⁺¹, with an appointment at 41⁺² to discuss induction. I used to believe that her carers had followed NICE’s guidelines. But the correct reading is that they had not done so.

So why does NICE not say, “Offer induction at 41⁺⁰ weeks, and let the exact timing take into account the woman’s preferences and local circumstances”? Perhaps they should.

Does it matter? If 2/3 of pregnancies are uncomplicated, 20% reach 41⁺⁰ weeks, and if the number needed to induce to prevent a stillbirth at 41⁺⁰ weeks is 500, induction then rather than at 42⁺⁰ would save 160 baby lives each year in UK. In practice the gains will be smaller because a lot of inductions are already offered at 41⁺⁰, but there would be some easy wins.

Jim Thornton

* The average pregnancy lasts 40 weeks^{+0 days}. So 41⁺⁰ is a week over the average, albeit well within the “normal” range. 42⁺⁰ is two weeks over the average. The current Danish standard 41⁺³ is  Term plus ten days.