Customized fetal growth charts that account for maternal characteristics could improve the identification of at-risk babies and reduce avoidable stillbirths, according to a study published by The BMJ on July 8. The research examined over 3 million NHS births across England and found that current one-size-fits-all fetal growth charts often misclassify babies as too small or too large, leading to missed cases at risk of stillbirth or unnecessary interventions.
The study highlights that fetal growth restriction increases the risk of adverse pregnancy outcomes, making early detection essential for mother and baby safety. Researchers from the Perinatal Institute in Birmingham compared different types of fetal weight charts—including Hadlock, Intergrowth-21st, World Health Organisation (WHO), Fetal Medicine Foundation (FMF), and the customizable GROW chart—across 3.2 million births between 2015 and 2025 in most NHS integrated care boards in England.
They found that using a customized chart such as GROW, which adjusts for factors like maternal weight and ethnic origin, provided more accurate data than universal unadjustable charts derived mostly from other countries. For example, the average rate of babies identified as small for gestational age at term ranged widely depending on the chart used: from 4.8% with Intergrowth to 17.2% with WHO and FMF charts, while customized GROW charts identified 12.3%. Unadjusted charts also showed wide variation between regions due to local population differences—a problem not seen with adjusted GROW charts.
The researchers acknowledged limitations including reliance on birthweight rather than ultrasound-estimated weight, but noted their findings covered about 90% of NHS areas in England. They called for urgent standardisation of growth chart use across the NHS.
The authors argued that rare but catastrophic outcomes may result from delayed recognition caused by inconsistent protocols at individual trusts. They proposed a coordinated national programme focusing on standardised assessment and real-time oversight to monitor quality and safety in maternity care.
