NHS England Halts Intergrowth Fetal Charts
NHS England has instructed maternity units to stop using Intergrowth 21 estimated fetal weight charts due to concerns they may underdiagnose
NHS England asked all maternity units in England to stop using Intergrowth 21 estimated fetal weight (EFW) charts in December 2025. This decision was made due to concerns about the charts' applicability to the NHS population, as analysis indicated they could lead to a lower detection rate of small-for-gestational-age (SGA) fetuses.
According to a correction issued by the Royal College of Obstetricians and Gynaecologists (RCOG) to its Green-top Guideline No. 31, this underdiagnosis risk means some fetuses that should receive enhanced surveillance might not. The correction clarifies which fetal growth charts are now recommended for clinical practice.
Recommended Fetal Weight Charts
The RCOG correction states that maternity providers in England should use specific EFW charts. The original Intergrowth EFW chart from 2017 should not be used. It employed a study-derived equation rather than the standard Hadlock equation. The Intergrowth project itself identified problems and updated its charts in 2020.
Providers are advised to use the Hadlock, World Health Organization (WHO), Fetal Medicine Foundation (FMF), or the Perinatal Institute GAP/GROW EFW charts. The 2020 version of the Intergrowth 21 chart, which is based on the Hadlock equation, may only be used under strict conditions.
| Chart Name | Key Detail | Status for Use |
|---|---|---|
| Intergrowth 21 (2017 version) | Used a study-derived equation | Should not be employed |
| Intergrowth 21 (2020 version) | Based on Hadlock three-parameter equation | Use only if underdiagnosis can be prevented |
| Hadlock EFW chart | - | Recommended |
| WHO EFW chart | - | Recommended |
| Fetal Medicine Foundation (FMF) EFW chart | - | Recommended |
| Perinatal Institute GAP/GROW EFW chart | - | Recommended |
The correction notes that using the 2020 Intergrowth chart requires a maternity care provider to ensure that SGA and fetal growth restriction are not underdiagnosed in their local population. Given the level of local data and analysis needed, the RCOG states it is unlikely most providers will be able to meet this condition. For more detailed clinical data and guidelines, clinicians can refer to the stats and injuries pages.
Challenges Beyond 40 Weeks
Assessing fetal growth at or beyond 40 weeks of gestation presents specific difficulties. The correction highlights that measuring fetal biometry, especially head circumference, becomes less accurate at this stage.
Some recommended EFW charts, namely the Hadlock and WHO charts, end at 40 weeks. Others, like the GROW chart, are based on extrapolated data. This period also carries an increased risk of stillbirth. Consequently, the management of suspected fetal growth disorders past 40 weeks should be decided on a case-by-case basis with input from senior clinicians. Further information on related protocols can be found in the fixtures section.
Research and Apology
The guideline correction cites supporting research, including a 2021 study by Sovio and Smith comparing estimated fetal weight centiles near term. It also references a 2019 Swedish population-based cohort study by Vieira and colleagues that examined birthweight centile thresholds using different charts. The RCOG has apologized for the error in the original guideline.
