Perinatal Characteristics and Automated Auditory Brainstem Response Screening Outcomes in Newborns: A Retrospective Hospital-Based Cohort Study

Background: Universal newborn hearing screening (UNHS) programs are essential for early detection of congenital hearing impairment. In community and secondary hospital settings, distinguishing true screening failures from protocol-driven risk referrals and tracking outpatient follow-up represent key operational challenges. Objective: To evaluate automated Auditory Brainstem Response (AABR) screening outcomes and explore their associations with delivery mode, anesthesia type, nationality, and selected perinatal characteristics in a retrospective newborn cohort. Secondary objectives were to describe protocol-driven risk referrals despite normal screening results and to assess incomplete screening due to loss to outpatient follow-up. Methods: This retrospective observational cohort study evaluated 406 consecutive singleton newborns undergoing universal AABR screening between 1 June 2024 and 31 May 2025 at a private secondary hospital in Istanbul, Türkiye. Screenings followed a multi-stage protocol using the MADSEN AccuScreen system (35 dB nHL click stimuli). Outcomes were classified into four mutually exclusive groups: (1) normal AABR without referral, (2) protocol-driven referral due to predefined hearing-loss risk factors despite a normal AABR, (3) final AABR refer (screening failure), and (4) incomplete screening/lost to outpatient follow-up. Primary exploratory analyses compared completed normal passes (n = 384) with final screen refers (n = 7) using exact tests. A post hoc sensitivity analysis was conducted treating all incomplete cases as screening refers (n = 22 vs. n = 384). Results: Among 406 singleton newborns, 343 (84.5%) passed AABR without referral, 41 (10.1%) passed AABR but were referred for audiological surveillance due to clinical risk factors, 7 (1.7%) had a final AABR refer result and were referred for diagnostic audiological evaluation, and 15 (3.7%) had an initial refer but defaulted before completing outpatient rescreening. In the primary analysis, lower gestational age showed a nominal association with a final AABR refer [median 37.0 weeks (IQR 36.5–38.0) vs. 38.0 weeks (IQR 38.0–39.0); p = 0.026]. In the sensitivity analysis incorporating all 15 incomplete cases (n = 22), this nominal association with lower gestational age was also observed [median 37.5 weeks vs. 38.0 weeks; p = 0.028]. Neonatal intensive care unit (NICU) admission (p = 0.018) and predefined risk factors (p = 0.004) showed nominal univariate associations with screening refer; after Holm adjustment for multiple comparisons, only the predefined risk factor composite remained below 0.05. Sex, delivery mode (cesarean vs. vaginal), and anesthesia type were not significantly associated with screening outcome; however, given the small number of events (n = 7), these findings should be regarded as statistically inconclusive rather than definitive evidence of no effect. Among the 41 risk-referred infants, prolonged NICU hospitalization (>5 days) was the predominant referral criterion (n = 29, 70.7%). In the post hoc worst-case sensitivity analysis, general anesthesia compared with regional anesthesia (p = 0.014) and Syrian nationality compared with Turkish nationality (p = 0.008) showed nominal associations with the hypothetical expanded refer outcome, illustrating the sensitivity of these findings to incomplete follow-up. Conclusions: In this retrospective hospital-based cohort, only seven newborns had a final AABR refer result, limiting the precision of association estimates. Although lower gestational age and NICU admission showed nominal associations with final screening refer, only the predefined hearing-loss risk factor composite remained statistically significant after adjustment for multiple comparisons. Fifteen newborns (3.7%) did not complete outpatient rescreening, identifying a measurable gap in follow-up documentation. These findings support improved screening-completion tracking and warrant validation in larger cohorts with confirmatory audiological outcomes.