Abstract

Background: Assessment of the fetal nervous system - both in its anatomical structure and functional behaviour - has long been a challenge in perinatal medicine. Recent advances in ultrasound technology, especially 3D and 4D ultrasound, now allow detailed real-time observation of fetal anatomy and behavior. The development and maturation of the fetal brain in utero (and its continuity into extrauterine life) is a complex dynamic process: fetal neurobehavior is thought to follow a reproducible, gestational-age–dependent pattern that reflects neurological integrity. If normative fetal neurodevelopmental stages could be recognized and standardized, then deviations - abnormal neurobehaviors - could be identified, enabling prompt prenatal diagnosis of nervous-system pathology. Objective: The aim of this study was to emphasize the potential of 4D ultrasound–based fetal neurobehavioral evaluation (specifically with the Kurjak Antenatal Neurodevelopmental Test, KANET) in detecting abnormal neurobehavior prenatally, and to underline how this method may allow early identification of fetuses at risk for neurodevelopmental impairment. Methods: Review of the concept of fetal neurobehavioral assessment using 4D ultrasound. The KANET test applies 4D ultrasound to observe fetal behavior (movements, facial expressions, general/isolated movements) across gestation, akin to how neonates are neurologically assessed postnatally. By standardizing a scoring system for fetal behaviors relative to gestational age, KANET distinguishes between normal, borderline, and abnormal fetal neurobehavior. Evidence from multicenter studies and clinical/practice settings is considered to assess the feasibility and predictive value of KANET. Results: a) 4D ultrasound makes it possible to observe a wide repertoire of fetal behaviors (limb movements, facial expressions, mouth movements, hand-to-face, general movements), with increasing complexity and organization through gestation - reflecting central nervous system (CNS) maturation. PubMed+2De Gruyter Brill+2; b) Application of KANET in both low-risk and high-risk pregnancies (including growth-restricted and diabetic pregnancies) has shown significant differences in fetal behavior patterns. PubMed+2journaljammr.com+2; c) Postnatal follow-up in some studies found that fetuses with abnormal prenatal KANET scores indeed displayed adverse neurological outcomes - suggesting KANET’s potential as a predictive tool. PubMed+2PubMed+2; d) A recent systematic review (2025) found consistent evidence that behaviors observed via 4D ultrasound (e.g., yawning, hand-to-face, startle, general movements) increase in complexity between approx. 24–34 weeks gestation, coinciding with known neurodevelopmental milestones (e.g., thalamocortical connectivity). PubMed+1; e) However, despite growing evidence for structured fetal behavior as a marker of neural integration, the review cautions that such behaviors cannot yet be equated with consciousness or subjective awareness. PubMed+1.- Conclusion: The advent of 3D/4D ultrasound - and standardized tools like KANET - enables non-invasive prenatal assessment not only of fetal anatomy but also of functional neurodevelopment. Observing and scoring fetal behavior provides a promising avenue for early detection of neurodevelopmental abnormalities. While current evidence supports the use of KANET in clinical practice to identify fetuses at risk for neurodevelopmental impairment, interpretation should remain cautious: observed behaviors likely reflect maturation and neural integration but do not equate to consciousness. Further large-scale, long-term follow-up studies are needed to solidify the predictive validity and clinical utility of prenatal neurobehavioral assessment.

Key words: fetal neurobehavior, 4D ultrasound, prenata brain assessment, KANET, fetal neurodevelopment.