Impact of replacing Chinese ethnicity‐specific fetal biometry charts with the INTERGROWTH‐21^st standard

Abstract

Objective To assess the impact of adopting the st biometry standards in a Chinese population.Design Retrospective cohort study.Setting A teaching hospital in Hong Kong.Population A total of 10 527 Chinese women with a singleton pregnancy having a second-or third-trimester fetal anomaly or growth scan between January 2009 and June 2014.Methods Z-scores were derived for fetal abdominal circumference (AC), head circumference (HC), and femur length (FL) using the INTERGROWTH-21 st and Chinese biometry standards.Pregnancies with aneuploidy, structural or skeletal abnormalities, or that developed pre-eclampsia were excluded. Z-scores were stratified as <2.5th, <5th, <10th, >90th, >95th, or >97.5th percentile. Birthweight centile, adjusted for gestation and gender, was categorised as ≤3rd, 3rd to ≤5th, 5th to ≤10th, and >10th. Pairwise comparison and the McNemar test were performed to assess biometry Z-score differences and concordance between the INTERGROWTH-21 st and Chinese standards.Main outcome measures The sensitivity of both the local and INTERGROWTH-21 st AC standards to identify pregnancies that were small-for-gestational-age (SGA) was assessed.Results INTERGROWTH-21 st AC, HC, and FL Z-scores were significantly lower than those obtained using our local reference for AC, HC, and FL (P < 0.0001 for all). The proportion of fetuses with biometry in the <2.5th, <5th, <10th, >90th, >95th, or >97.5th percentiles was statistically significant (P < 0.01 for all

Are selection criteria for healthy pregnancies responsible for the gap between fetal growth in the French national Elfe birth cohort and the Intergrowth‐21st fetal growth standards?

“…Our finding that the differences in growth parameters between the sample restricted to women fulfilling the IG selection criteria and the overall population were very small is relevant for the current debate on growth standards vs. references. It shows that population selection is not an explanation for the differences between the IG standards and fetal growth in the ELFE cohort and is also unlikely to explain the differences found in other population‐based studies . More broadly, this finding challenges the relevance of distinguishing between growth “references” and “standards” for fetal growth monitoring, at least in high‐income settings where malnutrition is low and access to health services is high.…”

“…It shows that population selection is not an explanation for the differences between the IG standards and fetal growth in the ELFE cohort and is also unlikely to explain the differences found in other population-based studies. [10][11][12][36][37][38] More broadly, this finding challenges the relevance of distinguishing between growth "references" and "standards" for fetal growth monitoring, at least in high-income settings where malnutrition is low and access to health services is high. A recent study within a Norwegian multi-ethnic population which applied IG criteria also showed that this did not reduce ethnic differences in fetal growth parameters.…”

“…The IG fetal growth norms also face criticism for not accurately reflecting fetal growth in a growing number of studies, either because too few or too many fetuses are classified under the 10th percentile or too few are classified as over the 90th percentile . One reason for these discordant findings may be population selection.…”

“…[6][7][8] Proponents of these standards claim that they are intended to describe normal child growth and therefore are not expected to "fit" all populations. 9 The IG fetal growth norms also face criticism for not accurately reflecting fetal growth in a growing number of studies, either because too few 10 or too many fetuses 11 are classified under the 10th percentile or too few are classified as over the 90th percentile. 12 One reason for these discordant findings may be population selection.…”

Birth‐weight differences at term are explained by placental dysfunction and not by maternal ethnicity

“…The controversy surrounding this issue has increased following recent publications suggesting that prescriptive fetal growth standards would be less sensitive in identifying small‐for‐gestational‐age (SGA) fetuses and adverse perinatal outcome than the corresponding locally‐developed fetal growth charts. In contrast, other studies have reported that the use of locally developed fetal growth standards was associated with a disproportionate number of fetuses being classified as SGA, resulting in unnecessary fetal surveillance.…”