Our weeks are made of 7 days. An entirely arbitrary unit of measurement, based on an idea that 7 is magical, so there are 7 continents, 7 seas, 7 days of the week. Or maybe because you can easily divide a lunar month by 4, in fact it isn’t totally clear why there are 7 days in a week. It is hidden in the mists of time, the majority of human cultures use the 7 day week. But what if it had been 5? What if the Aztec system of 20 day periods, divided into 5 day weeks, had taken over?

2 day weekends and 3 days of work sounds like fun. Of course the duration of a pregnancy in Aztec land would be 56 five-day weeks, and then what we now refer to as 25 weeks gestation would become 35 five-day Aztec weeks. Neonatal survival becomes less and less likely as we descend to 34 Aztec weeks, or 33, and so on. But imagine if you were in an Aztec country,and the local paediatric society had recommended that “33 weekers” were not viable, because survival is too low, or impairment is to high (actually they don’t ever explicitly say why 33 weekers should not get active care) . Imagine if you were denied active intervention because you were only at “33 weeks” and 4 days, and told to go away until you hit 34 weeks. You could maybe just fly to Canada to find that you were suddenly viable, as you were 24 weeks and 1 day in 7-day weeks.

You could be forgiven for being a bit angry about your local paediatric society’s guidelines, especially when you realize that your ultrasound performed at 16 Aztec weeks was only accurate to within about one 5-day week, 95% of the time.

I’ve been thinking about this recently. Especially after the publication of the NICHD network data on active treatment, and how it changes by weeks of gestational age. One of the graphs from that publication shows that active intervention at 22 and 23 weeks stays relatively unchanged as a proportion of deliveries until just before the end of the week.

Which is odd, but I think easy to understand. We have become used to thinking of babies in terms of whole numbers of weeks of gestation. So a baby of 23 0/7 is thought of as being the same as 23 5/7. But once the baby is within 48 hours of the next big number, at which point they may have had steroids because of crazy hospital policies, based on 7 being the magical number, our attitudes start to change. I would be fascinated to know when the mothers got their steroids, and if that is really the cause of the jump up in intervention rates.

I would also be fascinated to see what the pattern would be in Aztec land.

One other thing that I think this shows, is that shared decision-making is currently a sham. Surely if mothers were adequately informed, and truly participated in the decisions, rather than having them imposed by physicians or by hospital practice, then there would be a progressive gradual increase in intervention as gestational age advanced. Mothers would have no reason for suddenly deciding at 23 weeks and 5 days that their baby should have active intervention.

I am sure that the physicians who resuscitate 100% of the babies at 22 weeks, and those that resuscitate none of them, all think they practice shared decision-making. But clearly if there are no babies being resuscitated, (once there are significant numbers of mothers in the data) then the values of the physicians and the care team are being imposed on the families. If the decision was truly shared, then there would be at least a few who occasionally received active intervention.