FM12 Designation of small-for-gestational age according to 7 fetal growth charts in England’s National Health Service: retrospective analysis of 3.2 million births
Fetal Medicine
Information
OBJECTIVE The latest guidelines for antenatal management of small-for-gestational age (SGA) babies do not specify which fetal growth charts to use. We investigated the SGA screen positive rates of standards in current use in England.
METHOD Retrospective cohort study of electronic data recorded as part of routine care, for 38 of the 42 NHS Integrated Care Boards (ICBs) in England. Rates of SGA (<10th centile) weight at birth, were calculated according to 7 fetal weight standards: Hadlock1, Intergrowth-21st (IG21; versions 20172 and 20203), World Health Organisation4 (WHO), Fetal Medicine Foundation5 (FMF), GROW Lite6 (UK average) and GROW7 (customised for maternal height, weight, parity and ethnic origin).
RESULTS The cohort included 3,201,199 women with singleton pregnancies delivered between 2015 and 2025. There was wide variation in maternal characteristics between ICBs, including ethnic origin (English: mean 65.6%, range 19.8-92.2) and high body mass index (BMI>30: mean 24.8%, range 16.3-29.4). The range of centiles across all ICBs was wider for all population-average standards and correlated significantly with ethnicity and maternal size. The customised GROW standard had SGA (<10) rate of 13.4% and narrowest range across ICBs (11.6-15.2%). Average SGA (<10) rates for term births (>37.0 weeks) were lowest for IG21(2017) (4.8%), highest for WHO and FMF (both 17.2%) and 12.3% with GROW (see Table).
CONCLUSION Uncustomised fetal weight charts in current NHS use do not reflect the average, distribution and variation of birthweight in our maternity population and are likely to miss fetuses at risk due to restricted growth.
METHOD Retrospective cohort study of electronic data recorded as part of routine care, for 38 of the 42 NHS Integrated Care Boards (ICBs) in England. Rates of SGA (<10th centile) weight at birth, were calculated according to 7 fetal weight standards: Hadlock1, Intergrowth-21st (IG21; versions 20172 and 20203), World Health Organisation4 (WHO), Fetal Medicine Foundation5 (FMF), GROW Lite6 (UK average) and GROW7 (customised for maternal height, weight, parity and ethnic origin).
RESULTS The cohort included 3,201,199 women with singleton pregnancies delivered between 2015 and 2025. There was wide variation in maternal characteristics between ICBs, including ethnic origin (English: mean 65.6%, range 19.8-92.2) and high body mass index (BMI>30: mean 24.8%, range 16.3-29.4). The range of centiles across all ICBs was wider for all population-average standards and correlated significantly with ethnicity and maternal size. The customised GROW standard had SGA (<10) rate of 13.4% and narrowest range across ICBs (11.6-15.2%). Average SGA (<10) rates for term births (>37.0 weeks) were lowest for IG21(2017) (4.8%), highest for WHO and FMF (both 17.2%) and 12.3% with GROW (see Table).
CONCLUSION Uncustomised fetal weight charts in current NHS use do not reflect the average, distribution and variation of birthweight in our maternity population and are likely to miss fetuses at risk due to restricted growth.
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