PO02 High SGA rates by uncustomised fetal weight standards in South Asian pregnancies at term do not represent increased stillbirth risk
Pregnancy Outcome
Information
OBJECTIVE Babies of South Asian mothers have an increased risk of being stillborn. Their intrauterine weight is also more likely to be small-for-gestational-age (SGA) according to universal fetal growth standards which do not adjust for ethnicity. We examined whether the two observations are related at term, where designation of SGA is most consequential for management.
METHODS We studied a routinely recorded database of South Asian singleton term pregnancies from 83 NHS trusts/health boards in 2023-25, with 65,340 term deliveries including 61 stillbirths. SGA (<10th centile) at delivery was assessed using the following fetal weight standards: Hadlock1, Intergrowth2, WHO3, as well as GROW4 which was customised for ethnicity, maternal height, weight and parity. Stillbirth risk was calculated for groups designated as SGA by each standard.
RESULTS 7,584 fetuses (11.6%) were SGA at delivery according to GROW, and included 24 stillbirths (RR: 4.9; CI 3.0-8.3). The SGA rates were higher according to each universal standard: Hadlock 24.5%, WHO 31.1%, Intergrowth 16.1%. The additional pregnancies designated SGA by each of these standards were not associated with increased stillbirth risk: Hadlock +8584 (RR 1.8, CI: 0.9-3.9), WHO +12,760 (RR 1.9, CI: 0.97-3.8) and Intergrowth +3628 (RR 1.8, CI: 0.6-5.1).
CONCLUSION Higher SGA rates in South Asian pregnancies according to one-size-fits-all fetal weight standards are not associated with increased stillbirth risk, and indicate that the wrong standard is being used. Artificially inflated SGA rates may lead to unnecessary interventions and divert attention from more likely causes of increased stillbirth risk in ethnic minority groups.
METHODS We studied a routinely recorded database of South Asian singleton term pregnancies from 83 NHS trusts/health boards in 2023-25, with 65,340 term deliveries including 61 stillbirths. SGA (<10th centile) at delivery was assessed using the following fetal weight standards: Hadlock1, Intergrowth2, WHO3, as well as GROW4 which was customised for ethnicity, maternal height, weight and parity. Stillbirth risk was calculated for groups designated as SGA by each standard.
RESULTS 7,584 fetuses (11.6%) were SGA at delivery according to GROW, and included 24 stillbirths (RR: 4.9; CI 3.0-8.3). The SGA rates were higher according to each universal standard: Hadlock 24.5%, WHO 31.1%, Intergrowth 16.1%. The additional pregnancies designated SGA by each of these standards were not associated with increased stillbirth risk: Hadlock +8584 (RR 1.8, CI: 0.9-3.9), WHO +12,760 (RR 1.9, CI: 0.97-3.8) and Intergrowth +3628 (RR 1.8, CI: 0.6-5.1).
CONCLUSION Higher SGA rates in South Asian pregnancies according to one-size-fits-all fetal weight standards are not associated with increased stillbirth risk, and indicate that the wrong standard is being used. Artificially inflated SGA rates may lead to unnecessary interventions and divert attention from more likely causes of increased stillbirth risk in ethnic minority groups.
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