The importance of illumination - the case of covert retention

I want to discuss the issue of covert retention of urine after birth. It’s one of those things that we learn or hear about, and accept, until we dig a bit deeper. At which point we find that it’s not quite as straightforward as we might have been led to believe. This blog post is an updated version of an article in which I looked at this.

Over the years, I have become increasingly aware of just how many of the tenets of the medical approach to childbirth are based not on research evidence or sound reasoning. Instead, they are rooted in accidents of history, seemingly arbitrary choices or quirks of numerical fate. I am often asked why the cut-off limit for the administration of postnatal anti-D is 72 hours. The answer — at least as I understand it — has nothing to do with there having been research studies that tested a variety of limits and discovered that this was the cut-off point before which anti-D provided the most effective coverage. It is, instead, because this was the time frame used in some of the early research studies, which used prisoners as subjects, rendering timing of access a key issue.

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The assessment of post-birth urination

Another example of an area in which the values seem arbitrary is the assessment of urination in women who have recently given birth. As Champion (2013) highlighted, the values that are used in this assessment are arbitrary in at least two ways. The first being that the numbers change from study to study and between areas of service provision. This is probably because, secondly, each time someone needs to define a numerical value in order to develop their own research study protocol or practice guideline, they have no option but to either choose someone else’s arbitrarily-arrived-at number or merrily add their own guesswork into the mix. Concerned about the rapid introduction of a guideline for bladder care, she set out to look at the evidence for this. Among other things, the guideline requires that, if a woman hasn’t passed urine within six hours of birth, she should be encouraged to do so and, if she can’t, catheterisation should be considered. Some areas require a specific volume of urine to be passed; usually 200-250ml.

How did we get here?

Now, one might think that things we consider problematic and write guidelines about are deemed to be problematic because, well, they have caused problems. But a key concern about this guideline was that it seemed to have come out of nowhere, along with concerns about something called ‘covert retention’. That term describes a situation where the bladder hasn’t fully emptied. It may or may not be normal, but we’ll come back to that. So, with that in mind, was the volume of urine used to determine so-called covert retention in these guidelines found to be problematic in a study exploring the experiences of postnatal women who had difficulty passing urine?

No.

Was it based on women reporting or experiencing a particular problem? On midwives seeing a growing problem on postnatal wards, or in women who had just given birth at home or in birth centres?

No.

Oh. OK then, was the volume of urine that is considered normal (and has thus become the target at which women aim when filling their measuring jugs) carefully chosen from the results of a study that looked at the amount of urine postnatal women normally passed after birth?

Still no.

Covert retention

“It is worth remembering that ‘covert retention’ was only found because researchers went looking for it, not because women were troubled by it.” (Champion 2013)

There are several other possibilities that could have formed a logical base on which to build the aforementioned practices, but which did not. I won’t keep listing them, for I imagine that you have taken my point by now. I was particularly struck when I read that the definitions of postnatal urinary retention have been extrapolated from a pathological situation which likely differs in several key areas from that in which postnatal women’s bladders find themselves (Yip et al 2004). This is very worrying to me, because I first became interested in what was happening in relation to the notion of covert urinary retention in the postnatal period when approached by some midwives who were concerned that there were moves afoot to begin screening all women in their area for this with the use of ultrasound. When one looks at the evidence, it is hard to see that there is even a problem, let alone one which would justify such an invasive, expensive and potentially pointless screening programme in order to find it. As Champion (2013) notes, “it is worth remembering that ‘covert retention’ was only found because researchers went looking for it, not because women were troubled by it.” She concluded that, “the evidence to support a guideline saying that women should pass 200mls (or any specific volume) or urine within six hours of birth is weak.” (Champion 2013).

Myriad examples

There are myriad examples of situations where the values that determine what happens to women and babies have been arrived at in an arbitrary fashion. These raise questions about who decides such things, and on what basis such decision are made. But the issue of alleged covert urinary retention is concerning enough in itself and the problem can be boiled down really easily to the one issue that really matters: the fact that the underpinning facts are anything but factual. There is no long and noble literature detailing how the number of millilitres of urine that denotes covert urinary retention in women who have recently given birth was arrived at. There has — to my knowledge, but please comment if you know differently — been no consensus conference in which the great and the good pooled their clinical experience while drinking wine in a hot tub.

Instead, the numbers used appear to have been extrapolated from an area that is related in some ways but absolutely irrelevant in others. Then they are repeated and published enough to help them on their way to becoming such a part of the literary furniture that we will soon forget that there was no real basis for their use in the first place. As has happened in the case of those myriad other examples too.

Arbitrary ideas

It is fascinating (and also alarming) to dig deeper and discover just how many of the ideas that underpin the way in which we approach childbirth arose in a relatively arbitrary fashion, often with incredibly good intentions. I am not suggesting for a moment that anyone is setting out solely to naff off women or midwives by the proffering of plastic jugs. This is a genuine attempt to solve what is perceived to be a real potential problem. Yet the first step in such an endeavour must surely be to determine whether a problem actually exists, with an emphasis on ensuring that this is the case before we set up arbitrary targets at which we then make all women’s bodies aim. Or could we return to a less standardised approach wherein midwives care for and assess women on an individual basis, using their skills and knowledge to determine if and when a problem may be present?

It is true that there is so much conflicting evidence that it is easy to lose one’s way in the ocean of information now available on almost any topic. But evidence is not necessarily the key in this case. Surely it is the careful application of thought, intelligence and — dare I say it — common sense that is paramount? Numbers and findings on their own are no good; we need light in which to consider them and context in which to locate them.

This kind of illumination, I would suggest, is gained only by carefully thinking about what we think we know.

Champion P (2013). The childbearing bladder: an amazingly adaptable organ. EM 4(6): 17-23.

Yip SK, Sahota D, Pang MW et al (2004). Postpartum urinary retention. Acta Obstetricia et Gynecologica Scandinavica 83(10):881-91.