Impact of replacing Chinese ethnicity-specific fetal biometry charts with the INTERGROWTH-21(st) standard

• Published in: BJOG : an international journal of obstetrics and gynaecology Vol. 123 Suppl 3; pp. 48 - 55
• Main Authors: Cheng, Yky, Leung, T Y, Lao, Tth, Chan, Y M, Sahota, D S
• Format: Journal Article
• Language: English
• Published: England 01-09-2016
• Subjects: Adult; Biometry - instrumentation; Birth Weight; Diagnostic Errors; Ethnic Groups; Female; Fetal Development; Fetal Growth Retardation - diagnosis; Fetal Weight; Growth Charts; Head - diagnostic imaging; Head - embryology; Hong Kong; Humans; Infant, Small for Gestational Age; Medical Overuse; Predictive Value of Tests; Pregnancy; Pregnancy Trimester, Third; Reference Standards; Retrospective Studies; Risk Assessment; Ultrasonography, Prenatal - standards; fetal biometry; INTERGROWTH-21st; Chinese; small-for-gestational-age; pregnancy; ultrasound measurements
• ISSN: 1471-0528
• DOI: 10.1111/1471-0528.14008

To assess the impact of adopting the INTERGROWTH-21(st) biometry standards in a Chinese population.
Retrospective cohort study.
A teaching hospital in Hong Kong.
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.
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.
The sensitivity of both the local and INTERGROWTH-21(st) AC standards to identify pregnancies that were small-for-gestational-age (SGA) was assessed.
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). A total of 1224 (15.5%) of the scans at 18-22 weeks of gestation had AC, HC, or FL below the 3rd percentile of the INTERGROWTH-21(st) standard.
Adopting the INTERGROWTH-21(st) standard would lead to a significant number of fetuses being at risk of misdiagnosis for small fetal size, particularly when using HC and FL measures.
INTERGROWTH-21(st) biometry assessment in Chinese leads to fetuses being at risk of misdiagnosis of small fetal size.