Fetal adrenal microvascular index and adrenal volume in late-onset fetal growth restriction: A prospective observational study.

Objective

This study evaluates the fetal adrenal gland microvascular index (MVI) and adrenal volume in late-onset fetal growth restriction (FGR) using MV-Flow and three-dimensional Extended Imaging Virtual Organ Computer-Aided Analysis and assesses their associations with neonatal outcomes.

Methods

This prospective observational study at a single tertiary center (July 2024-August 2025) included 58 fetuses with late-onset FGR and 65 healthy controls. FGR was defined as abdominal circumference or estimated fetal weight <3rd percentile or 3-10th percentile with Doppler abnormalities. Fetal adrenal MVI (microvascular perfusion relative to organ size) and adrenal volume were measured during routine ultrasound. Group comparisons, logistic regression, receiver operating characteristic analyses, and correlation analyses were performed.

Results

Fetal adrenal MVI was significantly higher in the FGR group (38.9% vs. 23.1%, P < 0.001). MVI was independently associated with FGR (odds ratio 1.175, 95% confidence interval [CI] 1.108-1.247, P < 0.001). MVI showed good discriminative ability for FGR (area under the receive operator characteristic curve = 0.876, 95% CI 0.815-0.937), with a cutoff of 25.3% (94.8% sensitivity, 64.6% specificity). Although adrenal volume was lower in the FGR group (4.37 vs. 5.50 cm3, P = 0.016), this difference disappeared after normalization to estimated fetal weight (P = 0.149) and abdominal circumference (P = 0.558). Lower adrenal volume was associated with neonatal intensive care unit admission independently of gestational age and birth weight (partial r = -0.252, P = 0.010).

Conclusion

Fetal adrenal glands show reduced absolute volume but increased microvascular perfusion in FGR cases. Adrenal MVI is a size independent marker of late-onset FGR, whereas reduced adrenal volumes largely reflects smaller fetal size.