(537) Fetal growth restriction diagnosed at anatomy ultrasound is associated with an increased risk of stillbirth

Objective: Although fetal growth restriction (FGR) is associated with an increased risk of stillbirth, the data are limited regarding the stillbirth risk for FGR diagnosed in early second trimester. We aimed to determine the association between FGR diagnosed at anatomy ultrasound and risk of stillbirth.

Study Design: We conducted a retrospective cohort study of singleton pregnancies delivered between 2017 to 2022 who had both a first trimester dating ultrasound and an anatomy ultrasound between 18 0/7 and 23 6/7 weeks. Cases with known major structural or genetic abnormality or congenital infection were excluded. FGR was defined as estimated fetal weight (EFW) or abdominal circumference (AC) below the 10^th percentile for gestational age. Primary outcome was occurrence of stillbirth. Patient characteristics were compared, and logistic regression models were performed to estimate adjusted odds ratios (aORs) for stillbirth accounting for demographic factors and maternal medical conditions.

Results:
Of the 6871 patients that met the inclusion criteria, 197 (2.9%) were diagnosed with FGR at the anatomy ultrasound. Patients in the FGR group were more likely to be Black or Asian, younger, and delivered at an earlier gestational age when compared to those without FGR. Fewer male fetuses were reported in the FGR group (38.1% vs 50.6%, p=0.001). There were no significant differences in rates of chronic hypertension, hypertensive diseases of pregnancy, diabetes, obesity, autoimmune disease, or COVID-19 during pregnancy between the two groups (Table 1). The rate of stillbirth was higher in the FGR at anatomy ultrasound group (3.6% vs 0.7%, aOR 5.18 (95%Cl 2.31-11.64)) with stillbirth diagnosed at an earlier gestational age (22.4 weeks vs 29.2 weeks, OR 0.88, 95% CI 0.75-1.03) compared with the no FGR group.


Conclusion: Diagnosis of FGR in fetuses without known structural or genetic abnormality at anatomy ultrasound was independently associated with an increased risk of stillbirth.