Anthropometry and pregnant and Lactating women (esp.MUAC)

I am not sure why you put scientific in quotes.

It is unclear whether you want to know whether we have seen research or whether you are looking for a reading list.

This is some related material at:

http://www.en-net.org.uk/question/169.aspx

http://www.en-net.org.uk/question/261.aspx

http://www.en-net.org.uk/question/215.aspx

http://tng.brixtonhealth.com/node/37

If you are after some reading ... you might try:

http://www.ncbi.nlm.nih.gov/pubmed/

and searching on "MUAC pregnancy" or "MUAC birth outcomes" or "MUAC maternal outcomes" or "MUAC maternal health"?

This is not really my area of expertise but I will give it a go ...

Ignoring gender, pregnancy, and lactation for a moment ... the problem is one of selecting cases of acute malnutrition in adults.

BMI is a poor indicator as it is strongly by body-shape. There are ways to correct this but they are not considered practicable for most purposes. This leaves use with MUAC as the only practicable indicator.

BMI is also problematic in pregnancy because it has a weight component. Even if we could use BMI in adults we could not use it for pregnant adults. Again we are left with MUAC as the only practicable indicator.

I think questions such as:

- MUAC is not changing during pregnancy;
- MUAC is not changing between pregnancy and lactation period
- MUAC is not changing during lactation

Are not that useful. They are, at best, interesting detail. At worst they are confusing detail.

The issue is one of finding a case-defining threshold. There are different ways of doing this. One in norm-referencing ... we use some statistical property of a distribution to define a threshold as we do with (e.g.) W/H z-score < -2 in children. The other is criteria-referencing ... we find a threshold below which a negative outcome becomes likely as we do with (e.g.) MUAC < 115 mm in children. I prefer the latter method as it selects individuals at risk. The problem is complicated by the need for a universal measure. If is possible (e.g.) that maternal weight or BMI is predictive of a negative outcome in all populations but the threshold at which risk increases to unacceptable levels is likely to differ between populations and individuals within the same population. The concentration has been on MUAC because there is some evidence that this is more universal than BMI (i.e. finding of low MUAC being predictive of a negative outcome are more common and more consistent than BMI).

We also need to define the population and the adverse outcomes. For this question we have a population of pregnant women but what do we have for negative outcomes? This could be (I guess) ... maternal death, pre-term birth, still birth, low birthweight, low chest circumference at birth, death of baby within three days, death of baby within one months ... it could be a long list.

I think that most work has been done on low birthweight. A brief look on PubMed found:

http://www.ncbi.nlm.nih.gov/pubmed/18638377
http://www.ncbi.nlm.nih.gov/pubmed/18094737
http://www.ncbi.nlm.nih.gov/pubmed/17230285
http://www.ncbi.nlm.nih.gov/pubmed/19880445
http://www.ncbi.nlm.nih.gov/pubmed/17195768
http://www.ncbi.nlm.nih.gov/pubmed/15980024
http://www.ncbi.nlm.nih.gov/pubmed/10021785

I advise you to search on your outcomes of interest.

It seems to me that there is a scientific consensus that low MUAC is a strong predictor of low birth weight (and other negative outcomes) bur I think that there has been little work on finding a threshold. This is probably why the usual 210mm (sometimes a bit higher) threshold is used (this theshold is for female adults regardless of PLW status). Just a brief look through the literature suggest that this may be too low and something like 260 mm might be better.

This is an interesting question and I am very glad you raised it. I think that there is a need for further work on this. The issue is not whether MUAC < 210 is a bad thing. There is good evidence for that in non-pregnant / non-lactating women. The issue is whether that threshold is sensitive enough for PLWs.

I think that the ENN moderator should canvas the opinions of MCH experts on this issue and report the results here.

Can others comment on this?

Thanks for those references.

The suggestion to raise the threshold is based on evidence from the peer-reviewed literature. The risk of a negative outcome such as low birthweight or maternal mortality does increase with decreasing MUAC and increases at levels of MUAC above 210 mm.

As a first stab ... if some mothers lose 10 mm during pregnancy then we should perhaps (as a start) raise thresholds by 10 mm. There is a also evidence from still-births and neonatal deaths that lactation reduces MUAC. We might, therefore, like to raise our threshold again. If we start with 210 mm we might end up admitting at 230 mm so as to prevent post-partum wasting.

My suggestion of 260 mm is based solely on the "brief look on PubMed" in my previous reply. My recall is that some of the studies referenced found increased risk of low birth weight at 270 mm and 260 mm. I would certainly want a more thorough technical review, some experience with pilot programs to investigate operational details and workload implications, followed by an expert group meeting before a solid recommendation. I think that this is something that could be organised by ENN or the WHO (or a collaboration between them). A brief review of available evidence suggests that we probably do not need further studies to arrive at a rational decision so the cost of a review will not be great,

BUT ... We need to bear in mind that the change we are contemplating here will increase sensitivity so we may end up treating some mums that do not need treatment but we will reduce the number of mums that need treatment that we fail to treat. If increasing the threshold will not damage other program activities (e.g. by increasing workload and damaging CMAM coverage) then the change is safe. We could safely do this now.

Ethnic differences in MUAC have not been sufficiently studied to determine whether a single set of MUAC thresholds could be used in all ethnic groups. The evidence from children suggests that a single set of thresholds could be used in all ethnic groups. This could be an issue addressed by a formal review.