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(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 < 3rdpercentile, or EFW or AC < 10th percentile
with abnormal blood flow. Doppler blood flow abnormalities in the ISUOG
guideline included abnormal uterine artery pulsation index (PI)
> 95th percentile, abnormal umbilical
artery PI > 95th percentile, and abnormal
brain-placental ratio < 5th percentile. The
definition of SGA newborn was birth weight lower than the
10th percentile of neonatal growth standards.
A composite ANO included one of these adverse outcomes: neonatal
umbilical arterial blood pH<7.1, 5-minute Apgar
score<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
< 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.