The magnitude rather than the rate of decline in fetal growth is a stronger risk factor for perinatal mortality in term infants

•Of note, ≥50th percentile fetal growth decline is associated with late fetal growth restrictions.•Of note, ≥50th percentile fetal growth decline is strongly associated with perinatal mortality.•The risk of fetal demise is related to the magnitude of decline and not the rate of decline.•Neonatal morbidity is not significantly associated with fetal growth decline.•The magnitude of fetal growth decline is important when determining the timing of birth. Prenatal diagnosis of an infant suspected of having fetal growth restriction is important because of its strong association with perinatal mortality and morbidity. The current Delphi consensus criteria include a decline of >50th percentiles in fetal growth when diagnosing late fetal growth restriction; however, the evidence underpinning this criterion is limited. This study aimed to analyze the relationships among the magnitude of decline in fetal growth and stillbirth, perinatal mortality, and adverse neonatal outcomes. This cohort study of 15,861 pregnancies was conducted at the Mater Mother's Hospital in Brisbane, Australia. The decline in fetal growth was calculated as a drop in either estimated fetal weight or abdominal circumference percentiles between 2 ultrasound scans performed after 18 weeks of gestation. Relationships between declining fetal growth and the outcomes were, firstly, analyzed as a continuous variable and, if significant, further assessed with the rate of decline and different magnitudes of decline, compared to the referent category (change in growth of ±10 percentiles between scans). The 3 categories of growth decline were >10th to