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Using the same methods and conceptual approach as the WHO child growth standards, the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project developed international growth and size standards for fetuses for clinical interpretation of routinely taken ultrasound measurements and for comparisons across populations.
- Neurodevelopmental milestones and associated behaviours are similar among healthy children across diverse geographical locations
- Postnatal growth standards for preterm infants: the Preterm Postnatal Follow-up Study of the INTERGROWTH-21st Project
- International Fetal Growth Standards - latest charts available
It would be useful to calculate (from your raw data) an estimated fetal weight at each point of fetal measurement using e.g. the Hadlock formula for HC AC and FL. Using the same methodology it should be possible to produce an EFW chart with the centiles defined. Practising obstetricians (endorsed by the RCOG) are using EFW rather than AC as the measurement to determine whether to manage the fetus as small.
I agree with Simon jenkinson that it would be useful to have an EFW chart with the centiles defined. That's the way most obstetricians do in Obstetrical Practice. Are you working for it?
Fetal measurements could be automatically obtained from 2D or 3D ( http://www.sofka.com/AFHB.html ). In the case of 3D, the weight could also be estimated from the soft tissue measurements, such as arm and thigh.
Yes we are currently working on the EFW charts as these are what clinicians are most used to using in clinical practice, however they are often more prone to error than individual measurements.
In most places the measurements that go into the Hadlock formula (i.e FL, AC, etc) are also reported against local charts (e.g the Chitty chart in the UK). This can lead to the situation where all measurements are above the 10th centile when considered individually, yet the EFW is less than the 10th centile according to Hadlock. We are exploring options of both applying the Hadlock formula to our data as well as developing new formulae to try and see if there is any way around this however we also recognise that any small errors in individual measurements will be compounded in an EFW formula.
Keep looking at this website for updates!
I am convinced that IG21 fetal growth standards are the best available methodologically and have gone some way to convince quite a few of my colleagues, including opinion leaders in Australia and New Zealand of this too. However I am disappointed that downloadable charts seem to be slow in coming forth from the IG21 consortium. While individuals can produce spreadsheets and graphs from the regression formula (and z-scores) given in the Lancet publication using computer programs such as MS Excel, many potential IG21 fetal growth standard users don't have the time or expertise to do this. Can you please help?
EFW charts development:
My colleague Dr Michael Bethune suggested this approach: use the IG21st 40 week newborn weight distribution (mean and SD, so known coefficient of variation) and extrapolate backwards into earlier GA (and forwards to 41 and 42 weeks too as needed) using Hadlock proportionality curves. This should preserve the "prescriptive" or "standard" quality and avoid description which reflects local, sometimes biased populations, particularly drawing from high risk pregnancies (whether clinically recognised risk for stillbirth or from enthusiastic volunteer 40-something year old pregnant women who "feel" 28 years old but are realistically likely at higher risk of stillbirth than the IG21 participants so probably don't grow fetuses the same way as younger women.)
EFW charts development:
Has anybody plotted an EFW chart as suggested above using the IG21 data. Would like to have a copy if available. Is the consortium coming out with one such chart as mentioned earlier.