Updated birth weight centiles for England and Wales

Area of Science:

• Perinatal Health
• Neonatal Growth Monitoring
• Public Health Surveillance

Background:

• Current UK-WHO birth weight-for-gestational age charts may not accurately reflect contemporary UK birth data.
• Accurate growth assessment is crucial for identifying intrauterine growth restriction (IUGR) and ensuring timely intervention.

Purpose of the Study:

• To construct and validate updated sex-specific birth weight-for-gestational age centile charts for the UK.
• To compare these new centiles with the existing UK-WHO charts.
• To enhance the identification of infants affected by IUGR and those requiring increased postnatal monitoring.

Main Methods:

• Secondary analysis of national birth data from England and Wales (2013-2015).
• Construction of centiles using the lambda-mu-sigma method (GAMLSS package in R) on over 1.2 million births.
• Validation using over 640,000 singleton births.

Main Results:

• The new MBRRACE-UK centiles demonstrated good performance in the validation sample.
• Compared to UK-WHO charts, new centiles identified a higher proportion of term infants below the second birth weight centile (1.97% vs 1.32%).
• At earlier gestational ages, UK-WHO charts overestimated the proportion of infants below centiles, especially at the lower birth weight spectrum.

Conclusions:

• Updated birth weight-for-gestational age centiles for the UK have been successfully constructed and validated.
• These charts will improve the national surveillance of perinatal mortality by better identifying IUGR.
• Clinicians will benefit from more accurate identification of neonates requiring enhanced monitoring post-birth.