62 - Differentiating Early and Late-Onset Fetal Growth Restriction: Implications for Pathophysiology, Outcomes, and Management

Publication Number: 2059.62

Carletta P. Hensley, University of Missouri-Columbia School of Medicine, Wentzville, MO, United States; Andrea Goldstein, University of Missouri-Columbia School of Medicine, Columbia, MO, United States; Maya Demirchian, University of Missouri-Columbia School of Medicine, Columbia, MO, United States; Jean R. Goodman, University of Missouri-Columbia, Columbia, MO, United States; Akshaya J. Vachharajani, University of Missouri, Columbia, MO, United States

Background: Fetal growth restriction (FGR), defined as estimated fetal weight or abdominal circumference below the 10th percentile for gestational age, complicates up to 10% of U.S. pregnancies and remains a leading cause of perinatal morbidity and mortality. FGR is classified as early ( < 32 weeks) or late-onset (≥32 weeks), with uteroplacental insufficiency recognized as a shared principal driver of impaired fetal growth. Despite similar management strategies and risks of intrauterine demise, neonatal complications, developmental delay and cardiometabolic disease, the two phenotypes differ in clinical presentation.

Objective: We aimed to assess etiologic differences and outcome patterns between early and late-onset FGR, to better characterize and manage these distinct clinical phenotypes.

Design/Methods: A retrospective chart review of obstetric records from a tertiary academic medical center was conducted following IRB approval. A total of 522 patients were identified: 311 with early-onset FGR and 211 with late-onset FGR. Maternal demographics, placental pathology, and neonatal outcomes were analyzed using Chi-square and Mann-Whitney U tests as appropriate, with significance defined as p < 0.05.

Results: Maternal analysis demonstrated that late-onset FGR was more commonly associated with prenatal marijuana use, whereas early-onset FGR had no predominant maternal risk factors (Fig. 1). Placental and umbilical assessments indicated late-onset FGR displayed features suggestive of chronic placental insufficiency, while early-onset FGR exhibited findings consistent with vascular abnormalities and placental maldevelopment (Fig. 2). Prenatal growth profiles and neonatal outcomes revealed that late-onset FGR was more likely to have an ultrasound diagnostic of FGR within one week of delivery and to result in birth weight classified as small-for-gestational-age. Early-onset FGR more frequently resolved prior to delivery but had higher risk of preterm birth, lower birth weight, neonatal morbidity, congenital anomalies, NICU admission, prolonged NICU stay, and infant death prior to discharge (Fig. 3).

Conclusion(s): The association of late-onset FGR with maternal substance use and subtle placental pathology highlights the need for maternal risk factor modification and timely recognition of placental abnormalities. Early-onset FGR carries greater risk of neonatal morbidity and mortality, emphasizing the value of close monitoring, parental counseling and consideration of earlier intervention. These distinct clinical and pathological profiles have important implications for managing FGR-affected pregnancies and optimizing outcomes.

Figure 1. Maternal Factors by Early vs Late FGR
Comparison of maternal risk factor and complication profiles in early- versus late-onset fetal growth restriction (FGR).

Figure 2. Placental and Umbilical Pathology by Early vs Late FGR
Comparison of placental pathology, umbilical cord abnormalities, and amniotic fluid findings in early- versus late-onset fetal growth restriction (FGR).

Figure 3: Prenatal Growth Diagnostics and Neonatal Outcomes by Early vs Late FGR
Comparison of fetal growth patterns based on biometry and neonatal outcomes in early- versus late-onset fetal growth restriction (FGR).