Timing and severity of fetal growth restriction diagnosis and association with perinatal morbidity

Objective: In 2020, the Society of Maternal Fetal Medicine refined fetal growth restriction (FGR) diagnostic criteria by temporal (early-, <32 weeks; late-onset, ≥32 weeks) and measurement-specific definitions (severe, estimated fetal weight <3rd; mild, estimated fetal weight 3rd-9th percentile and/or abdominal circumference <10th percentile). Using these updated clinical definitions, we sought to determine the association of timing and severity of fetal growth restriction diagnosis with, and their discriminatory ability for, adverse pregnancy outcomes. Study Design: This retrospective cohort study included singleton, non-anomalous pregnancies with sonographic fetal growth restriction diagnosis at ≥180 weeksdays gestation from 5/2020-12/2021. We evaluated four FGR classification exposure groups: 1) early-onset, severe FGR; 2) early-onset, mild FGR; 3) late-onset, severe FGR; and 4) late-onset, mild FGR. Outcomes assessed were hypertensive disorders of pregnancy, preterm birth, and small-for-gestational age. Multivariable logistic regression estimated the odds of each outcome associated with each exposure, adjusted for maternal age, insurance, and parity. Receiver-operating characteristic analysis determined test characteristics for the ability of these FGR classification groups to identify the postnatal outcomes, using late-onset, mild FGR as the reference group. Results: Among 566 eligible pregnancies, early-onset, severe FGR had higher adjusted odds of hypertensive disorders of pregnancy (aOR 1.3, 95% CI 1.1-1.7), preterm birth (aOR 2.1, 95% CI 1.6-2.6), and small-for-gestational age (aOR 1.6, 95% CI 1.3-1.9), compared to late-onset, mild FGR. Late-onset, severe FGR also had higher adjusted odds of preterm birth (aOR 7.2, 95% CI 2.9-18.3) and small-for-gestational age (aOR 5.8, 95% CI 2.5-13.6). Odds of adverse pregnancy outcomes were similar with early- and late-onset mild FGR. Overall, discriminatory ability of these FGR classification groups for adverse pregnancy outcomes were poor. Conclusion: Early- and late-onset, severe FGR (versus late-onset, mild FGR) are positively associated with, but have poor discriminatory ability for, adverse pregnancy outcomes.

Publication History

Received: 19 September 2024

Accepted after revision: 03 December 2025

Accepted Manuscript online:
15 December 2025