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\begin{document}

\title{Comparison of three different international fetal growth restriction
definitions in Chinese population}



\author[1]{Huijing Zhang}%
\author[1]{yongbing guo}%
\author[1]{Meixia Shang}%
\author[2]{Weiwei Zhang}%
\author[3]{Chunli Feng}%
\author[4]{Hongyan Zhao}%
\author[1]{yu sun}%
\author[1]{Huixia Yang}%
\affil[1]{Peking University First Hospital}%
\affil[2]{Aerospace Center Hospital}%
\affil[3]{Tongliao Second Renmin Hospital}%
\affil[4]{Chengde Central Hospital}%


\vspace{-1em}



  
  \date{May 26, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
\textbf{Background} Fetal growth restriction (FGR) is defined
differently by the American College of Obstetrics and Gynecology (ACOG),
Society for Maternal-Fetal Medicine (SMFM), and the International
Society of Ultrasound in Obstetrics and Gynecology (ISUOG).
\textbf{Objective} The purpose of this study was to investigate the
predictive effect of three different diagnostic criteria of FGR on
small-for-gestational-age (SGA) and adverse neonatal outcome (ANO), so
as to find a better FGR-definition for Chinese population. \textbf{Study
Design} The clinical data of singleton pregnancy who received regular
pregnancy care and gave birth at the Department of Obstetrics and
Gynecology of Peking University First Hospital from January 1, 2021, to
June 30, 2021 were collected. FGR cases were determined according to
three different diagnostic criteria by ACOG, SMFM, or ISUOG. The primary
outcome was the prediction of SGA and a composite ANO. SGA was defined
as neonatal birth weight less than 10 \textsuperscript{th} percentile.
An ANO included one of these adverse outcomes: neonatal umbilical
arterial blood pH \textless{} 7.1, 5-minute Apgar score\textless{}7,
acute respiratory distress syndrome (ARDS), intraventricular hemorrhage,
and neonatal convulsion, and transfer to the neonatal intensive care
unit (NICU). The specificity, sensitivity, negative predictive value
(NPV) and positive predictive value (PPV) of the different diagnostic
criteria for SGA and ANO were compared. The discriminatory capacities of
the three FGR-definitions were compared using the area under
receiver-operating-characteristics curves (AUC). \textbf{Results} A
total of 2340 cases were included in this study, and 115 (4.9\%), 63
(2.7\%), and 48 (2.1\%) cases of FGR were diagnosed using the diagnostic
criteria issued by the SMFM, ACOG, and ISUOG respectively. There were
147 (6.28\%) cases of SGA neonates. The SMFM criteria had higher
sensitivity (40.82\% vs 24.49\%, 20.41\%) for SGA compared to the ACOG
and ISUOG criteria. On the contrary, the ISUOG criteria had a higher
specificity (99.18\% vs 97.49\%, 98.77\%) than the SMFM and ACOG
criteria for predicting SGA. A total of 127 (5.43\%) cases were
complicated with ANO. All three definitions had low sensitivity for ANO
(17.32\%, 12.6\%, 11.81\%) and high specificity of 95.8\%, 97.88\% and
98.51\%. The AUCs of SMFM for predicting SGA (0.692) and ANO (0.566)
were slightly higher than those of ACOG (0.616, 0.552) and ISUOG (0.598,
0.552). \textbf{Conclusion} The predictive value of the SMFM and ISUOG
definition for SGA and ANO was better than that of the ACOG criteria. In
Chinese population, the discriminatory capacities of SMFM FGR definition
were superior compared to the other two definitions.%
\end{abstract}%



\sloppy


Comparison of three different international fetal growth restriction
definitions in Chinese population

Huijing Zhang\textsuperscript{\#1}, Yongbing Guo\textsuperscript{\#1},
Meixia Shang\textsuperscript{2}, Weiwei Zhang\textsuperscript{3}, Chunli
Feng\textsuperscript{4}, Hongyan Zhao\textsuperscript{5}, Yu
Sun\textsuperscript{1}, Huixia Yang*\textsuperscript{1}

\textsuperscript{\#}Huijing Zhang and Yongbing Guo contributed equally
to this article

\textsuperscript{1}Department of Obstetrics and Gynecology, Peking
University First Hospital, Beijing, 100034, China

\textsuperscript{2} Department of Statistics, Peking University First
Hospital, Beijing, 100034, China

\textsuperscript{3}Department of Ultrasound, Aerospace Centre Hospital,
Beijing, China

\textsuperscript{4} Department of Ultrasound, Tongliao Second Renmin
Hospital, Inner Mongolia, China

\textsuperscript{5} Department of Obstetrics and Gynecology, Chengde
Central Hospital, Hebei, China

*Corresponding author: Huixia Yang, Department of Obstetrics and
Gynecology, Peking University First Hospital, Beijing, China, 100034.
Email address: yanghuixia@bjmu.edu.cn.

The authors declare that they have no competing interests.

This research received no specific grant from any funding agency in the
public, commercial, or not-for-profit sectors.

Word Count: Abstract: 401 words; Main text: 2387 words.



\textbf{Tweetable statement}

Fetal growth restriction (FGR) is the leading cause of intrauterine
fetal death, neonatal death, and short-term and long-term complications
worldwide. It is difficult to evaluate the potential growth of a fetus.
Therefore, different countries and associations have developed different
guidelines to screen for fetuses with suspected FGR. The purpose of this
study was to compare the ability of different FGR definitions to predict
small-for-gestational-age (SGA) and adverse neonatal outcomes (ANO), so
as to figure out a more suitable definition for Chinese population.

In this respective study, a total of 2340 cases were included. Among
them, 115 (4.9\%), 63 (2.7\%), and 48 (2.1\%) cases of FGR were
diagnosed using the diagnostic criteria issued by the SMFM, ACOG, and
ISUOG respectively. There were 147 (6.28\%) cases of SGA neonates. The
SMFM criteria had higher sensitivity (40.82\% vs 24.49\%, 20.41\%) for
SGA compared to the ACOG and ISUOG criteria. All three definitions had
low sensitivity for ANO (17.32\%, 12.6\%, 11.81\%) and high specificity
of 95.8\%, 97.88\% and 98.51\%. The AUCs of SMFM for predicting SGA
(0.692) and ANO (0.566) were slightly higher than those of ACOG (0.616,
0.552) and ISUOG (0.598, 0.552).

\textbf{Comparison between Fetal Growth Restriction Definitions}

\textbf{AJOG at a Glance}

\textbf{Why was this study conducted}

Fetal growth restriction (FGR) is the leading cause of intrauterine
fetal death, neonatal death, and short-term and long-term complications
worldwide. It is difficult to evaluate the potential growth of a fetus.
Therefore, different countries and associations have developed different
guidelines to screen for fetuses with suspected FGR. The purpose of this
study was to investigate the predictive effect of three different
diagnostic criteria of FGR on small-for-gestational-age (SGA) and
adverse neonatal outcome (ANO), so as to find a better FGR-definition
for Chinese population.

\textbf{Key Findings}

The criteria by Society for Maternal and Fetal Medicine (SMFM) had
higher sensitivity (40.82\% vs 24.49\%, 20.41\%) for small-for
gestational age (SGA) compared to the American College of Obstetrics and
Gynecology (ACOG) and International Society of Ultrasound in Obstetrics
and Gynecology (ISUOG) criteria. On the contrary, the ISUOG criteria had
a higher specificity (99.18\% vs 97.49\%, 98.77\%) than the SMFM and
ACOG criteria for predicting SGA. All three definitions had low
sensitivity for ANO (17.32\%, 12.6\%, 11.81\%) and high specificity of
95.8\%, 97.88\% and 98.51\%. The AUCs of SMFM for predicting SGA (0.692)
and ANO (0.566) were slightly higher than those of ACOG (0.616, 0.552)
and ISUOG (0.598, 0.552).

\textbf{What does this add to what is known}

This is the first study from Chinese population to discuss the
discriminatory capacities of different FGR definitions. The predictive
value of the SMFM and ISUOG definition for SGA and ANO was better than
that of the ACOG criteria. In Chinese population, the discriminatory
capacities of SMFM FGR definition were superior compared to the other
two definitions.

\textbf{Abstract}

\textbf{Background} Fetal growth restriction (FGR) is defined
differently by the American College of Obstetrics and Gynecology (ACOG),
Society for Maternal-Fetal Medicine (SMFM), and the International
Society of Ultrasound in Obstetrics and Gynecology (ISUOG).

\textbf{Objective} The purpose of this study was to investigate the
predictive effect of three different diagnostic criteria of FGR on
small-for-gestational-age (SGA) and adverse neonatal outcome (ANO), so
as to find a better FGR-definition for Chinese population.

\textbf{Study Design} The clinical data of singleton pregnancy who
received regular pregnancy care and gave birth at the Department of
Obstetrics and Gynecology of Peking University First Hospital from
January 1, 2021, to June 30, 2021 were collected. FGR cases were
determined according to three different diagnostic criteria by ACOG,
SMFM, or ISUOG. The primary outcome was the prediction of SGA and a
composite ANO. SGA was defined as neonatal birth weight less than
10\textsuperscript{th} percentile. An ANO included one of these adverse
outcomes: neonatal umbilical arterial blood pH \textless{} 7.1, 5-minute
Apgar score\textless{}7, acute respiratory distress syndrome (ARDS),
intraventricular hemorrhage, and neonatal convulsion, and transfer to
the neonatal intensive care unit (NICU). The specificity, sensitivity,
negative predictive value (NPV) and positive predictive value (PPV) of
the different diagnostic criteria for SGA and ANO were compared. The
discriminatory capacities of the three FGR-definitions were compared
using the area under receiver-operating-characteristics curves (AUC).

\textbf{Results}A total of 2340 cases were included in this study, and
115 (4.9\%), 63 (2.7\%), and 48 (2.1\%) cases of FGR were diagnosed
using the diagnostic criteria issued by the SMFM, ACOG, and ISUOG
respectively. There were 147 (6.28\%) cases of SGA neonates. The SMFM
criteria had higher sensitivity (40.82\% vs 24.49\%, 20.41\%) for SGA
compared to the ACOG and ISUOG criteria. On the contrary, the ISUOG
criteria had a higher specificity (99.18\% vs 97.49\%, 98.77\%) than the
SMFM and ACOG criteria for predicting SGA. A total of 127 (5.43\%) cases
were complicated with ANO. All three definitions had low sensitivity for
ANO (17.32\%, 12.6\%, 11.81\%) and high specificity of 95.8\%, 97.88\%
and 98.51\%. The AUCs of SMFM for predicting SGA (0.692) and ANO (0.566)
were slightly higher than those of ACOG (0.616, 0.552) and ISUOG (0.598,
0.552).

\textbf{Conclusion}The predictive value of the SMFM and ISUOG definition
for SGA and ANO was better than that of the ACOG criteria. In Chinese
population, the discriminatory capacities of SMFM FGR definition were
superior compared to the other two definitions.

\textbf{Key words} : FGR; diagnostic criteria; SGA, ANO, Chinese
population

\textbf{Introduction}

Fetal growth restriction (FGR) refers that the fetus has not reached its
growth potential due to the influence of certain factors (such as
placenta, chromosomes, and infection etc.). It is the leading cause of
intrauterine fetal death, neonatal death, and short-term and long-term
complications worldwide \textsuperscript{(1; 2; 3)}. In clinical
practice, it is difficult to evaluate the growth potential of a fetus,
because it is not pragmatic to record the percentile of fetal biometrics
and the estimated fetal weight (EFW) at different gestational
weeks\textsuperscript{(4)}. In addition, the ability to predict the
occurrence of adverse complications in a fetus due to FGR is relatively
limited \textsuperscript{(5)}.

Therefore, different countries and associations have developed different
guidelines to screen for fetuses with suspected FGR. The American
College of Obstetrics and Gynecology (ACOG) defines FGR as an EFW less
than the 10th percentile.\textsuperscript{(6)}. The Society of Maternal
and Fetal Medicine (SMFM)\textsuperscript{(7)} and the Royal College of
Obstetrics and Gynecology (ROCG)\textsuperscript{(8)} include abdominal
circumference (AC) in the assessment. According to the Delphi consensus
criteria, a consensus on the definition of FGR was established in
cooperation with global experts.\textsuperscript{(9)} The International
Society of Ultrasound in Obstetrics and Gynecology (ISUOG) cited this
definition to screen FGR.\textsuperscript{(10)}. The discuss on which
definition is more practical has been a hot point in recent
years\textsuperscript{(11; 12; 13; 14)}.

The purpose of this study was to compare the ability of different FGR
definitions to predict small-for-gestational-age (SGA) and adverse
neonatal outcomes (ANO), so as to figure out a more suitable definition
for Chinese population.

\textbf{Materials and Methods}

Study design and participants

This study retrospectively collected the clinical data of pregnant woman
who received routine pregnancy care and gave birth at the Department of
Obstetrics and Gynecology of Peking University First Hospital from
January 1, 2021, to June 30, 2021. We included all singleton pregnancies
during the period. The exclusion criteria were as follows: fetal major
structural abnormalities, chromosomal abnormalities and missing data
(Figure 1). This study was approved by the Ethics Committee of Peking
University First Hospital (2013-572). Informed consent was obtained from
all participants involved in the study.

Protocols and definitions

In this study, demographic data and clinical characteristics of all
enrolled subjects were collected, including maternal age, height,
weight, body mass index (BMI), gravida, parity, pregnancy method
(spontaneous / in vitro fertilization and embryo transfer (IVF-ET)),
maternal complications during pregnancy (pregestational diabetes
mellitus, gestational diabetes mellitus, gestational hypertension,
preeclampsia, chronic hypertension, chronic hypertension with
preeclampsia, nephropathy, autoimmune diseases such as lupus
erythematosus, rheumatoid arthritis, antiphospholipid syndrome, and
Sjogren's syndrome, thyroid diseases, and placental umbilical cord
abnormalities such as single umbilical artery and velamentous placenta),
gestational age at delivery, delivery method, and results of ultrasound
examinations during pregnancy. Neonatal outcome included neonatal
1-minute and 5-minute Apgar scores, umbilical arterial blood pH value,
admission (or not) to the neonatal intensive care unit (NICU) and
hospital stays, admission (or not) to the pediatric ward and hospital
stays, need for mechanical ventilation and phototherapy, neonatal
hypoglycemia, acute respiratory distress syndrome (ARDS),
intraventricular hemorrhage (IVH), anemia, necrotizing enterocolitis,
retinopathy, sepsis, convulsions, and pneumonia.

The gestational age was dated by the last menstrual period (LMP) or
assisted reproduction technology dating. If LMP was unknown or the
period was irregular, the first trimester ultrasound would be used. The
Hadlock formula III was used to calculate the EFW\textsuperscript{(15)}.
Three guidelines were used to define FGR: (1) the ACOG criteria for FGR:
EFW less than the 10th percentile; (2) The SMFM criteria for FGR: EFW or
AC less than the 10th percentile; (3) The ISUOG criteria for FGR: EFW or
AC \textless{} 3\textsuperscript{rd}percentile, or EFW or AC \textless{}
10\textsuperscript{th} percentile with abnormal blood flow. Doppler
blood flow abnormalities in the ISUOG guideline included abnormal
uterine artery pulsation index (PI) \textgreater{}
95\textsuperscript{th} percentile, abnormal umbilical artery PI
\textgreater{} 95\textsuperscript{th} percentile, and abnormal
brain-placental ratio \textless{} 5\textsuperscript{th} percentile. The
definition of SGA newborn was birth weight lower than the
10\textsuperscript{th} percentile of neonatal growth standards.

A composite ANO included one of these adverse outcomes: neonatal
umbilical arterial blood pH\textless{}7.1, 5-minute Apgar
score\textless{}7, acute respiratory distress syndrome (ARDS),
intraventricular hemorrhage, neonatal seizures, and admission to the
neonatal intensive care unit (NICU).

Statistical analysis

We used SAS 9.4 for the statistical analysis. Kolmogorov-Smimov
normality test checks the continuous data for normal distribution. If
the data complied with the normal distribution, measurement data are
expressed as the mean (standard deviation). Comparisons between groups
were performed using the variance analysis. If the data was not
consistent with the normal distribution, measurement data were expressed
as the median (quartile). Comparisons between groups were performed
using the Kruskal-Wallis H test. Categorical data are expressed as the
number (percentage). The chi-square test (or Fisher's exact test) was
used for comparisons between groups. P \textless{} 0.05 was considered
statistically significant.

The sensitivity, specificity, positive predictive value and negative
predictive value of ACOG, SMFM and ISUOG for neonatal SGA and ANO were
calculated using the fourfold (2X2) contingency table. The
discriminatory capacities of three FGR definitions to predict outcome
SGA and ANO was compared using the area under
receiver-operating-characteristics curves (AUC). Risk ratio (RR) and
95\% confidence interval (CI) to predict SGA and ANO were also compared.

\textbf{Results}

After excluding data that met exclusive criteria, a total of 2340 cases
were included for final analysis. Among whom, the number of FGR cases
defined by SMFM definition, ACOG definition and ISUOG definition were
115 (4.9\%), 63 (2.7\%) and 48 (2.1\%) separately. Due to the
overlapping of these three definitions, those FGR cases identified by
ACOG and ISUOG were included in the cases defined by SMFM (Figure 2).
Therefore, there were 2225 cases in the non-FGR group.

As shown in Table 1, the incidences of preeclampsia in the FGR groups
according to different definitions were significantly higher than those
in the non-FGR group (13.91\%, 17.46\%, 29.17\% vs 1.39\%), so was the
preterm birth rate (26.96\%, 36.51\%, 50\% vs 6.2\%) .

Regarding the neonatal outcomes, there were 147 cases (6.28\%) of SGA
newborns. The incidence of SGA in the different FGR groups was
significantly higher than that in the non-FGR group (52.17\%, 57.14\%,
62.5\% vs 3.91\%). There were 127 foetus (5.43\%) who were complicated
with ANO. The incidence of ANO in the FGR group was higher compared to
the non-FGR group (19.13\%, 25.4\%, 31.25\% vs 4.72\%). Likewise, the
incidence of each neonatal complications in the different FGR group were
also higher than that in the non-FGR group (Table 2).

When comparing the discriminatory capacities of the three different
definitions for predicting SGA (Table 3), the SMFM criteria had the
highest sensitivity (40.82\% vs 24.49\%, 20.41\%), while the ISUOG
criteria had the highest specificity (99.18\% vs 97.49\%, 98.77. As for
the predictive value for a composite ANO, it was displayed that all
three definitions had low sensitivity (17.32\%, 12.6\%, 11.81\%) and
high specificity of 95.8\%, 97.88\% and 98.51\%. The AUCs of SMFM for
predicting SGA (0.692) and ANO (0.566) were slightly higher than those
of ACOG (0.616, 0.552) and ISUOG (0.598, 0.552)

\textbf{Comment}

\textbf{Main findings}

The number of FGR cases defined by SMFM definition, ACOG definition and
ISUOG definition were 115 (4.9\%), 63 (2.7\%) and 48 (2.1\%) separately.
There were 147 (6.28\%) cases of SGA neonates and 127 (5.43\%) cases
complicated with ANO. As for predicting SGA or a composite ANO, the SMFM
criteria had the highest sensitivity and NPV, while the ISUOG criteria
had the highest specificity and positive predictive value. The AUCs of
SMFM for predicting SGA (0.692) and ANO (0.566) were slightly higher
than those of ACOG (0.616, 0.552) and ISUOG (0.598, 0.552).

\textbf{Strengths and limitations}

This was a cross-sectional study that collected the clinical data of
pregnant women who had given birth at our center. All singleton
pregnancies were included during the period except those with fetal
structural or chromosomal abnormalities or missing data. Compared to the
other studies analyzed in the population high-risk for FGR, our data
tended to summarize and analyze the data in a general population. It was
because third-trimester growth ultrasound was part of routine prenatal
care late pregnancy ultrasound in China. Besides, this study compared
the three most common FGR definitions in one paper in order to make a
more comprehensive and convictive conclusion, thereby providing evidenct
on choosing the most suitable FGR definition for Chiense population.

However, this study has limitations. The primary and secondary outcomes
of this study only focused on the neonatal period, but not the long-term
complications. Therefore, we should continue to follow up on long-term
neurological development disorders and the incidence of cardiovascular
and metabolic diseases in the children with suspected FGR. Because the
number of early FGR cases in this study was relatively small, we did not
distinguish early FGR and late FGR in this study. In the future, we hope
to perform prospective studies and increase the sample size.
Additionally, this study mainly used the last ultrasound biometrics as
indexes to assess growth potential. However, obviously, according to the
core meaning of FGR, it would make more sense if the fetal growth curve
could be tracked during the whole pregnancy. Therefore, the next step
was to improve the FGR detection rate by studying longitudinal changes
in FGR.

\textbf{Interpretation}

In our study, the SMFM definition identified 115 cases (4.91\%) of FGR,
the ACOG definition identified 63 cases (2.7\%) of FGR, while the ISUOG
definition identified 48 cases (2.05\%) of FGR. However, when Molina et
al.\textsuperscript{(12)} and Roeckner et
al.\textsuperscript{(13)}analyzed the data of the Redefining Fetal
Growth Restriction (RFGR) project, the ACOG definition identified 8.63\%
(91/1055) of FGR cases, the SMFM definition identified 13.0\% (137/1054)
of FGR cases, and the ISUOG definition identified 5.2.\% (55/1055,
55/1054) of FGR cases, with percentages that were higher than the
incidence observed in this study. The reason of the higher incidence was
that the population enrolled in the RFGR program was at high risk of
developing FGR. High risk factors included uterine height inconsistent
with gestational age, hypertension, diabetes, and other chronic kidneys,
blood vessel, and hemoglobin diseases. In their study, pregnant women
with chronic hypertension and pre-pregnancy diabetes accounted for 14\%
and 8\% of the sample, respectively. Nevertheless, the samples in our
study were from the general population. The percentages of chronic
hypertension and pregestational diabetes mellitus in this study were
1.1\% and 1.3\%, respectively Furthermore, our institution offered third
trimester ultrasound as a routine protocol, which provided sufficient
ultrasound biometric information for the calculation of EFW in the late
pregnancy.

The reason why SGA was selected as a primary outcome is that SGA is
associated with ANO and adult cardiovascular diseases and metabolic
diseases \textsuperscript{(16; 17)}. In addition, it has a clear
definition (birth weight less than the 10th percentile). Therefore, many
studies have used SGA as one of the indicators of the accuracy of FGR
predictions.\textsuperscript{(11; 12; 13)}. The results from this study
indicate that the performance of the SMFM-FGR definition to predict SGA
was higher than those of the ACOG-FGR and ISUOG-FGR criteria (AUC: 0.69
vs. 0.62 and 0.60), mainly because the sensitivity of the SMFM-FGR
criteria to detect SGA was significantly higher than those of the
ACOG-FGR and ISUOG-FGR criteria (40.8\% vs. 24.5\%, 20\%). In 2018, Blue
et al. compared the ability of RCOG (same as SMFM-FGR) and ACOG criteria
for FGR to predict SGA and found that the SMFM-FGR criteria were
slightly better than those of the ACOG-FGR criteria (AUC: 0.78 vs.
0.76)\textsuperscript{(11)}. When comparing the SMFM-FGR and ISUOG-FGR
criteria, Roeckner et al. also found that the sensitivity of the
SMFM-FGR criteria to predict SGA was significantly higher than that of
the ISUOG-FGR criteria (54.7\% vs. 28.8\%), while the specificity was
slightly lower than that of the ISUOG-FGR criteria (93.3\% vs.
98.4\%)\textsuperscript{(13)}.

As is known that not all SGA cases are pathological. Most of SGAs are
constitutional. Using the SGA alone to assess compare the predictive
ability of different FGR definition was comprehensive. Considering that
FGR fetuses were at an increased risk of fetal and neonatal mortality
and complications due to their reduced growth potential, there were also
a few studies which used neonatal complications and mortality as primary
outcome, thereby the concept of composite ANO being
proposed\textsuperscript{(12; 13)}. When Molina et al. compared the
ability of the ACOG-FGR and ISUOG-FGR criteria to predict ANO, the
performance of the ISUOG-FGR criteria was superior to that of the
ACOG-FGR criteria (sensitivity: 10.1\% vs. 9.3\%; specificity: 95.5\%
\textgreater{} 91.5\%) \textsuperscript{(12)}. In our study, the
sensitivity of the ACOG-FGR criteria for predicting ANO was slightly
higher than that of the ISUOG-FGR criteria, but the specificity was
slightly lower, and the AUC of the two groups was similar (0.552). When
Roeckner et al. compared the SMFM-FGR and ISUOG-FGR criteria, they found
that, although the sensitivity of the SMSM-FGR criteria was higher than
that of the ISUOG criteria, the specificity was lower than that of the
ISUOG criteria, and the AUC of the two groups was 0.51 vs. 0.53. In this
study, the sensitivity of the SMFM-FGR criteria for predicting ANO was
higher than that of the ISUOG criteria, but the specificity was slightly
lower, and the final AUC for the SMFM-FGR criteria was slightly higher.
However, the differences in the medical resources and capabilities of
different institutions to deal with neonatal complications also led to
differences in ANO between studies.

Many studies have shown that different growth curves produce different
percentiles, thereby affecting the rates of detection of SGA and
LGA.\textsuperscript{(18; 19)}. In addition, different ethnic groups
have different growth potentials. For example, the average birth weight
of newborns in India is 2.9 kg, and the average birth weight of newborns
in the UK is 3.5 kg, with a difference of 600 g.\textsuperscript{(20)}.
Therefore, the National Institute of Child Health and Human Development
(NICHD) developed different growth curves for Caucasian, Black,
Hispanic, and Asian fetuses.\textsuperscript{(21)} Because there is no
authoritative local growth curve in China, the EFW percentile in this
study was determined based on the growth curve of Asian women developed
by the NIICHD\textsuperscript{(21; 22)}. The percentiles for newborns
are based on newly released data of newborns in nine cities in southern
and northern China in 2020.\textsuperscript{(23)}.

\textbf{Conclusion}

The predictive value of the SMFM and ISUOG definition for SGA and ANO
was better than that of the ACOG criteria. In China, the discriminatory
capacities of SMFM FGR definition were superior compared to the other
two definitions.

\textbf{Declaration section}

\textbf{Author contributions}

HJZ and YBG designed the research and drafted the manuscript. MXS
competed data analysis. WWZ, CLF and HYZ performed data collection and
literature search. YS and HXY were chief director of maternal and foetal
unit, and participated in its design and coordination. HXY provided
substantial edits and additions to the manuscript. All authors have
accepted responsibility for the entire content of this manuscript and
approved its submission.

\textbf{Funding statement.}

N/A

\textbf{Acknowledgement.}

None.

\textbf{Ethical approval and informed consent}

The study was conducted according to the guidelines of the Declaration
of Helsinki and approved by the Institutional Review Board of Peking
University First Hospital (protocol code 2013{[}572{]}). Informed
consent was obtained from all participants involved in the study.

\textbf{Data Availability Statement}

The data presented in this study are available on request from the
corresponding author.

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Figure and table legends

Figure 1 Overview of participants and FGR cases.

Figure 2 Composition of FGR group

Table 1 Demographic characteristics of the study population

Table 2 Neonatal outcomes

Table 3 The discriminatory capacities of the three different definitions\selectlanguage{english}
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\textbf{Hosted file}

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