Hidden and Delayed-Onset Hearing Loss in Children: Limitations of Newborn Hearing Screening and Future Directions.

Background/Objectives: Universal newborn hearing screening (UNHS) has significantly improved early detection of congenital hearing loss; however, discrepancies persist between prevalence at birth and latter childhood. These findings suggest the presence of hidden or delayed-onset forms of hearing impairments as a consequence of false-negative UNHS results. Methods: A bibliographic search was conducted in PubMed and Scopus for the period 2000-2026. A total of 103 papers met the inclusion criteria. This narrative review synthesizes recent literature on the limitations of current hearing screening strategies, focusing on false-positive and false-negative screening results, auditory neuropathy spectrum disorder (ANSD), genetic etiologies, and congenital cytomegalovirus (cCMV) infection as potential causes. Emphasis is placed on mechanisms underlying missed diagnoses and their clinical implications. Results: Current screening protocols, particularly those based on otoacoustic emissions (OAE), may fail to detect mild, progressive, or neural hearing loss. False-negative results are frequently associated with genetic mutations (e.g., GJB2), cCMV infection, and ANSD, whereas false-positive findings are often associated with transient middle ear conditions and early timing of testing. Automated auditory brainstem responses (AABR)-based approaches for hearing screening improve detection of neural dysfunction but are influenced by auditory pathway maturation, which may complicate interpretation of results in early life. Evidence indicates that a substantial proportion of sensorineural hearing loss identified later in childhood may not be detectable at birth using existing protocols. Conclusions: Hidden and delayed-onset sensorineural hearing loss represent significant challenges and limitations of current UNHS programs. Optimization of screening strategies-including broader implementation of AABR, integration of genetic and cCMV testing, and careful consideration of screening timing-may improve early detection of hearing loss and reduce long-term developmental consequences. Future updates of international guidelines should address these gaps to enhance diagnostic accuracy and clinical outcomes.