Which fetal biometry charts should be used? A large validation study in
Objective: To assess the impact of applying published fetal growth
references or standards in the Chinese mainland population and to
compare their ability to predict newborns small- for- gestational- age
(SGA). Design: Retrospective observational study. Setting: A tertiary
hospital in Shenzhen, a Chinese city with the most immigrants.
Population: All pregnant women (n=106,455) who booked for prenatal care
with ultrasound measurements for fetal biometry between 2012 and 2019.
Methods: A fractional polynomial regression model was applied to
construct Shenzhen fetal growth chart ranges for HC, BPD, AC, and FL.
The differences between Shenzhen charts and published charts were
quantified by calculating the Z-score. Main outcome measures: The impact
of applying these published charts was quantified by calculating the
proportions of fetuses with biometric measurements below the 3rd centile
of these charts. The sensitivity and area under the receiver operating
curves of published charts to predict neonatal SGA (birthweight
<10th centile) were assessed. Results: Following selection,
169,980 scans of fetal biometry contributed by 41,032 pregnancies with
reliable gestational age were analyzed. When using Hadlock references
(<3rd), the proportions of small heads and short femurs were
as high as 8.9% and 6.6% in late gestation, respectively. The
Intergrowth-21st standards matched those of our observed curves better
than other charts. When using AC<10th centile, all of these
references were poor at predicting neonatal SGA. Conclusion: Applying
Hadlock references could possibly misclassify a large proportion of
fetuses as SGA. Conversely, applying the Intergrowth-21st standard
appears to be a safe option in mainland China.