Recent weeks have seen the release of the results of the INTERGROWTH-21st Project and the publication of a number of papers and commentaries on the subject of the new international standards for fetal growth based on serial ultrasound measurements and the related international standards for newborn weight, length and head circumference by gestational age and sex.
In a nutshell, these standards are intended to be used around the world in everyday clinical practice, allowing comparisons across multiethnic populations. They are based on measurements taken from just over 20,000 babies in Brazil, China, India, Italy, Kenya, Oman, the UK and the USA. They are related to the WHO child growth standards published in 2006, which I coincidentally discussed at the time in a three part discussion article called Weighing the Dangers (with part 2 here and part 3 here).
As was the case following the publication of the child growth charts, there is a fascinating – and, I suspect, ongoing – debate to be had about the relative value of international standards versus standards based on smaller populations, although one of the main drivers for the projects that led to these charts was the fact that so many different charts were in use around the world. As Saugstad (2014) notes in the Lancet, the researchers found close agreement in the variables measured in babies born in all eight sites, although this commentary also raises two of the issues that concerned me the most about these charts. Neither of these are intended as a critisism of the research teams, who did an incredible job of collecting, collating and co-ordinating a massive amount of data.
The first issue is that the standard set in the research was to measure birthweight within 12 hours of delivery, which is a stunning achievement if you’re trying to get a trained researcher and specialised super-accurate scales to every newborn baby. But this same window is also quite a long timeframe within which to be measuring such an important variable given that there will be marked variations between how babies feed within that timeframe. We also know that it is normal for babies to lose weight in the first 48 hours after birth, but I couldn’t seen any reference made to the possible impact of these factors in the papers.
The second issue is also not the fault of the researchers, but relates to the important topic of early or late cord clamping. I was delighted to see this raised in the Lancet (2014):
“Investigators have reported mean increases in birthweight of 53 g10 and 101 g11 in term infants after delayed cord clamping; and this is a large increase from an epidemiological point of view. The difference in registered weight of a baby for whom cord clamping is delayed and weight taken immediately, versus the birthweight of a baby for whom the cord is clamped immediately and birthweight registered 12 h post-delivery, could be as high as 50 g per kg in the same baby. This is a substantial difference, especially given that Villar and colleagues’ study protocol called for no more than 5 g difference between the two measurements.” (Saugstad 2014)
I have to be honest and say that, because most of the women I work with do not want to have routine ultrasound scans, let alone the serial kind that are necessary for the application of the fetal charts, I am unlikely to be among the first people to get a sense for how these work in practice. But I would love to hear others’ thoughts on whether these charts divide practitioners as much as the last ones did…
Saugstad OD (2014). New growth charts for newborn babies. The Lancet 384(9946): 857-868