Birth weight discordance in very and extremely preterm twins and the risk of neonatal hearing loss

Objective: Birth weight (BW) discordant twins have an increased risk of mortality and morbidity. We aimed to study the effect of BW discordance on the risk of neonatal hearing loss (NHL) in very and extremely preterm twins.Study design: Results of the nationwide newborn hearing screening program in Dutch Neonatal Intensive Care Units and diagnostic examination were centrally registered between 2003 and 2021 and included in this study. We selected twins and singletons with a gestational age (GA) 24- < 32 weeks. Logistic regression analyses were applied to study the effect of BW discordance on the risk of NHL adjusted for BW, GA and sex. Singletons and concordant twins, defined as a BW discordance of <= 20 %, were used as two reference groups. BW discordance was further categorized as medium (>20-30 %) and high (>30 %).Results: In total, 3430 twins (2694 concordant, 428 medium and 308 high BW discordant), and 23,114 singletons were available. Smaller newborns of high BW discordant twins showed an increased risk of NHL compared to singletons (adjusted odds ratio with 95 % confidence interval was 3.56 (2.26-5.60)). Also, smaller newborns of medium and high BW discordant twins showed an increased risk of NHL compared to concordant twins (adjusted odds ratio with 95 % confidence interval were 1.97 (1.13-3.44) and 4.17 (2.56-6.82), respectively). No other statistically significant differences were found.Conclusion: BW discordance increased the risk of NHL in the smaller of the twin born very or extremely preterm. This risk increased as the weight difference increased.