The World Health Organisation Child Growth Standards (WHO 2006) are the long-anticipated graphical result of a longitudinal study which weighed and measured several thousand breastfeeding children from a variety of diverse but healthy backgrounds as they grew and developed. Claimed to be universally applicable, these charts are seen by many as a welcome replacement for their predecessors. As a result of this and the fact that they carry the weight of the World Health Organization name, they are being adopted by many countries and maternity care systems as the new gold standard for practice.
Given the comparative advantages that these charts offer, this is not surprising. For the past few decades, the growth of many babies (and, indeed, older children) was assessed in relation to charts which were based on the measurements of a smaller number of participants, often from very specific and limited populations. A good proportion of the babies whose measurements were included on these charts were formula-fed or experiencing a mixture of milks and feeding methods. As a consequence, we had no idea whether these charts accurately represented the growth of breast-fed babies and neither did we know whether they were useful in monitoring the growth of those babies who belonged to ethnic or socio-economic groups that were not represented in the original sample.
Because we have long perceived there to be differences between the growth rates and patterns of babies who are fed by different means and milks, the WHO charts have been hailed by some practitioners as more baby-friendly (and I mean this in the generic sense rather than specifically in relation to BFI). In depicting the average weights of a population of breastfed babies at different points in time, the charts are deemed to be more in alignment with the related ideas that breast milk is the best food for babies, that breasts are the best way of delivering this food and that babies are the best people to determine how much they need to eat and when. As one midwife commented, many people were looking forward to using these charts because they perceived that they would be ‘kinder’ to breastfeeding mothers and breast-fed babies.
Charts vs Reality
The reality for some mothers and midwives, though, has been a bit different from the perception, and a number of people perceive the charts to be somewhat less baby friendly than they had hoped. It seems that many people had hoped the charts would reflect the way in which many babies lose weight in the first days of life before regaining it as well as showing the different patterns in growth exhibited by breastfed babies compared to those fed on artificial milk. However, even some of those babies who are (in the opinion of their mothers and midwives) happily and heartily breastfeeding and not causing any concern on any other level can seem to be falling behind the average when their weight is mapped onto the charts during their first weeks of life. Many midwives are reassuring the mothers of these babies that there is no cause for concern. Knowing that common-sense and experiential knowledge are just as important as statistical charts, they point out that the baby who is feeding well, filling her nappy with appropriate amounts of the appropriate substances and exhibiting the normal behaviour of a well baby is not likely to be failing to thrive. They tell the baby’s mother that she is doing a fabulous job, that her breast milk is an amazing and wonderful fluid and that supplementation is absolutely not needed. These midwives are able to draw upon their experience of attending lots of healthy babies whose weight moves up and down relative to that of the population as a whole. They are not solely reliant on a chart to tell them how a baby is thriving, and their knowledge of normal growth patterns means that, if they are able, they take care in deciding when to weigh babies so as not to create undue concern.
This situation does, however, raise some interesting questions. The most important of which is: why do these charts not seem to correspond to reality? Was the study on which these charts were based somehow biased in one or more dimensions? Or have we been wrong in our observations and assumptions all this time? Are we missing an important point in the way we are using and interpreting the charts? Or is something else going on here?
A growing concern
Some midwives and mothers perceive that the WHO Child Growth Standards (2006) do not accurately represent the reality of the way in which breastfed babies grow. They have noticed that, when the weights of some of the babies who they perceive to be breastfeeding well are mapped onto the charts over the course of two or three visits, they can seem to be falling behind the average. This is of particular concern because, unlike their predecessors, the charts are based on the measurement of thousands of breastfed and well babies, and this situation thus raises a number of questions.
Evaluating the Methods
The idea that the WHO charts would be ‘kinder’ to breastfeeding mothers and breastfed babies is entirely understandable when considered in the light of the facts that previous charts included the measurements of babies who were bottle fed and that feeding different milks by different methods may lead to differences in growth rates. Statistics, however, are neither kind nor unkind; they are merely numbers which represent the data that humans set out to collect and analyse. One of the most important questions, then, concerns the need to look closely at the way in which the statistics were gathered. It is always possible that there will exist some means by which bias entered a research study and that this explains the lack of correlation between the charts and the reality.
The methods section of the WHO document, however, is hard to fault, and this is unsurprising given the level of thought and expertise that has gone into the development of these standards. Superb in its detail (if often so technical that one needs a high-level understanding of statistics to make sense of it), the study has clearly been well thought through and carried out. The measuring tools, checking methods and recording standards used in the studies on which the charts are based were impeccable. This means that we then need to consider the other side of the coin. If the study itself was so well conducted that we can find no problem in the way that the standards were compiled, could the fact that there is a discrepancy between the standards and what we perceive ourselves to know about the growth of breast-fed babies mean that our existing knowledge is inaccurate?
Time to Re-think Dogma?
In a recent article, Davies (2008) pointed out that some of the key “facts” relating to breastfeeding are in fact theoretical assumptions and that “we are still essentially naïve about the complexities of lactation” (43). This caused me to wonder whether the notion that babies lose weight after birth is another theoretical assumption which could be challenged. Perhaps this is true only for a very few babies? Or perhaps a fair number of babies put on a lot of weight in the first few days after birth and thus ‘cancel out’ the data gathered from those babies who lose weight? Neither of these possibilities corresponded to my own experiences, but it is entirely possible that my experiences are unusual and so, in the interests of research, I decided to ask around.
Some of the texts on evidence-based practice emphasise the importance of reporting on research even when the results do not show anything interesting, and it is with this in mind that I am proud to tell you that my asking around didn’t lead to my being able to offer a new theory of weight gain in the first few days. The midwives I asked were all interested by the question and prepared to reflect upon it. A few even said that it might be interesting to pay more attention to the proportion of babies who lost or gained weight in the first few days. Like me, however, the other midwives I talked to have all had experiences which have led them to believe that weight loss is totally usual and something that they would expect to see from their experience. They underpinned this with reference to knowledge about the physiological adaptations that a baby makes after birth and even the deepest and most open-minded reflection didn’t cause them to feel that maybe they should stop expecting to see weight loss in a good proportion of breast fed babies.
In any case, the WHO standards embrace the idea that it is normal for breast fed babies to lose weight during the first few days, and this is reflected in both the documentation and the charts themselves. This is, as I noted in the first part of this article, one of the most laudable aspects of this whole project, yet for all my looking at the methods and reflecting on practice and existing knowledge, I hadn’t answered the question which had set me off looking at all of this. I could see only one more possible avenue for exploration.
The final avenue
The discrepancies that some midwives and mothers noticed wherein the WHO Child Growth Standards (2006) seem to be showing that the weight of breastfed babies is falling behind the average during the first few days after birth were not easily explicable by the existence of bias in the methods used to carry out the research that led to the development of the standards. The high quality of this project would seem to imply that the charts are accurately representative of the reality experienced by the babies in the study. I also asked a number of midwives to reflect on their real-life experiences in order to check whether perhaps our existing knowledges and experiences can be challenged, and while there is always more that we can learn I found nothing to suggest that there is a significant problem with our current understanding either. This article explores some of the deeper issues that underpin the notion of developing global standards, and considers whether the research that has tested these standards in the field can offer insight into this situation.
The creation of a tool which is designed to be applied to children on a global scale is an essentially theoretical exercise; the testing of such a tool to see if it is actually useful is just as important. One of the first of the studies to test these standards in the field set out to evaluate the accuracy of the charts in four countries; Argentina, Italy, the Maldives and Pakistan (Onyango et al 2007). The researchers found high concordance between the WHO standards and the clinical assessments of those who care for each country’s babies, which provides further support of the usefulness and effectiveness of these standards.
Researchers from a number of other countries had access to recent, comparable data on child growth and, while they did not all carry out prospective studies designed solely to test the WHO standards, they were able to compare recent existing data with these standards. By contrast to the field testing of Onyango et al (2007), researchers in Hong Kong (Hui et al 2008) and the UK (Wright et al 2008) both found there was not complete agreement between the WHO standards and their own locally-gathered data. Could their findings be the key to understanding the discrepancies that mothers and midwives have identified?
The UK Problem
In order to answer this question, we need to look more closely at the discrepancies that were discovered. Wright et al (2008) used data gathered from a population of UK babies and found that, when the birth weights of those babies were mapped onto the WHO standards, the babies appeared to be larger than the global average. Despite the fact that the WHO standards take the normal weight loss of breastfed infants into account, UK babies tended to fall behind the WHO average over the next 2-4 months, which resulted in “a complex pattern of weight centile changes over the first year for the average UK child” (569). The researchers offer some interesting speculation about whether this discrepancy might be due to the fact that antenatal growth is better in the UK than in other countries. As interesting as this theory is, however, it is perhaps secondary to the fact that the findings of this study essentially answer the question that midwives have been raising since the global standards were adopted into practice.
Standards vs Reality
Even the best research methods are only as good as the ideas which underpin a study and, in this case, the key idea involves the notion of standardisation. These charts are offered as a global standard and, while it can be useful on some levels to see how one nation’s children are growing in relation to the rest of the world, this is not necessarily the kind of data that individual parents and practitioners need. Wright et al (2008) argue that the WHO standards are not appropriate for use in UK children until a few weeks after birth, not only because of the way they do not correlate with the UK data, but also because they do not include any data on pre-term babies. Whether this recommendation has any impact on the adoption (or otherwise) of these standards remains to be seen. But this does add more weight to the reassurances we can offer women who are worried about their baby’s progress, and perhaps we can also take heart from knowing that our own and women’s observations have been supported by the findings of a study which set out to discover the degree to which such standards actually relate to reality.
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A version of this article was originally published as Wickham S (2008). Weighing the Dangers Part 1. TPM 11(8):40, Wickham S (2004). Weighing the Dangers Part 2. TPM 11(9):44-45 and Wickham S (2008). Weighing the Dangers Part 3. TPM 11(10):48.
Davies, L (2008) Breastfeeding method and infant weight gain. TPM 11(7): 41-43.
Hui, LL, Schooling, CM, Cowling BJ et al (2007) Are universal standards for optimal infant growth appropriate? Evidence from a Hong Kong Chinese birth cohort. Archives of Disease in Childhood; 93: 561–5.
Onyango, AW, de Onis, M, Caroli, M et al (2008) FieldTesting the WHO Child Growth Standards in Four Countries. . Journal of Nutrition 137: 149-152.
WHO (2006) WHO Child Growth Standards based on length/height, weight and age. Acta Paediatrica Supplement 450: 76–85. Also available online at: http://www.who.int/childgrowth/en/
Wright, C, Lakshman, R, Emmett, P and Ong, KK (2008) Implications of adopting the WHO 2006 Child Growth Standard in the UK: two prospective studies. Archives of Disease in Childhood 93: 566-569.