One-size-fits-all foetal growth charts used in the NHS to monitor babies’ growth before birth often misclassify babies as being either too small or too large, which can lead to missed cases at risk of stillbirth or unnecessary interventions, finds a study of over 3 million NHS births across England published by The BMJ.
Foetal growth restriction (when a baby’s growth in the womb is slower than expected) increases risk of adverse pregnancy outcome, so spotting this during pregnancy and before the baby is born is essential for the safety of mother and baby. Its lack of recognition during pregnancy is the most frequent cause of avoidable stillbirth.
A variety of fetal weight charts are in use across hospitals in the NHS to define small and large for gestational age babies, including Hadlock, Intergrowth-21st (IG21), World Health Organisation (WHO), and Fetal Medicine Foundation (FMF) charts, all of which are not adjustable, and the customised GROW charts which can be personalised to each individual mother.
Researchers at the Perinatal Institute in Birmingham compared rates of babies identified as too small or too large according to different charts in 3.2 million births between 2015 and 2025 in 38 of the 42 NHS integrated care boards (ICBs) in England.
They found that using a customised growth chart that adjusts for the mother’s characteristics such as weight and ethnic origin, which affect the usual growth of the baby in the womb, provides more accurate and consistent data, improving safety and helping midwifery and medical staff to better identify babies requiring extra care during pregnancy.