2 MATERIALS AND METHODS
This was a retrospective study in the Fetal Medicine Center of the First
Affiliated Hospital of Chongqing Medical University in Chongqing, China,
between January 2017 and June 2020.
As this was a retrospective analysis
of routinely collected anonymized clinical data, the local Ethics
Committee confirmed that no ethical approval from the patients was
necessary in accordance with the national regulations.
SGA was defined as a customized birth weight between the 3rd and 10th
centiles, and FGR was defined as a birth weight < 3rd centile15. Late-onset fetal growth restriction (FGR) is
usually defined as that diagnosed >32 weeks of pregnancy.
Adverse perinatal outcomes included emergency cesarean section for
non-reassuring fetal status, 5-min Apgar score < 7 and
neonatal acidosis at birth 16. According to the ACOG
guideline 17, all of
the SGA with normal umbilical artery Doppler included in our study were
delivered at about 37 weeks of gestation. The gestational age (GA) was
determined according to the last menstrual period, the first-trimester
crown-rump length or the head circumference when the first ultrasound
examination was performed after 14 weeks of gestation.
The inclusion criteria for three groups were as follows: (1) singleton
gestation, (2) intact membranes, (3) absence of congenital or
chromosomal abnormalities, (4) absence of pregnancy complications (i.e.
hypertensive disorders, diabetes), (5) normal amniotic fluid, (6) the
UA-PI within the normal range for GA, (7) SGA and FGR were delivered at
37 ± 2 weeks and (8) an ultrasound examination, including fetal biometry
and UA velocities, was performed
at
37 ± 2 weeks for all fetuses. The parameters of UA velocities included
the umbilical artery end-diastolic velocity (UA-EDV), umbilical artery
peak systolic velocity (UA-PSV), umbilical artery mean diastolic
velocity (UA-MDV) and umbilical artery time-averaged maximum velocity
(UA-TAMXV).
The normality of the data was determined by Kolmogorov-Smirnov test.
Continuous variables were expressed as the means ± standard deviations
or the Medians (interquartile ranges) as appropriate. Categorical
variables were expressed as the numbers of cases. For multiple
comparisons, one-way analysis of variance (ANOVA) was performed for
continuous variables, and pearson’s chi-square test was performed for
categorical variables. Logistic regression analysis was performed to
identify the predictive factors of FGR. The predictive performance for
FGR was determined by receiver–operating characteristics (ROC) curve
analysis. P < 0.05 was considered to be statistically
significant. All P values were two-sided, and P values of
less than 0.05 were considered statistically significant. Statistical
analyzes were performed using SPSS version 21.0 (IBM Corporation,
Armonk, NY, USA) and MedCalc version 11.4.2 (MedCalc Software, Ostend,
Belgium).