Author's response to reviews Title:Mitochondrial mutation m.1555A>G as a risk factor for failed newborn hearing screening in a large cohort of preterm infants Authors:

conclusion: We agree and modified the conclusion accordingly. Minor revisions: Birth weight: OR for birth weight are given for 100 g increments. We modified the result section and table 1 accordingly. OAE/ABR: the method of hearing screening was not recorded in the GNN-datasets. Aminoglycoside administration: if tested separately (without m.1555A>G-carrier-status as a covariate) aminoglycoside administration is a significant risk factor for failed hearing screening at a global p-value of 0.015, but not if adjusted for multiple testing. Rate of failed hearing screening: Similar to the literature. An additional reference was included. Follow-up: 5-year-follow-up of GNN-infants who were born in 2009 or later will start in fall this year. We included this information in our manuscript. Cost effectiveness: This will depend on long term outcome. If the rate of permanent hearing loss is increased (inducing lifetime cost up to 1,000,000$) it is easy to demonstrate cost-effectiveness even if only a small number of infants is affected. We prefer not to discuss cost effectiveness in our manuscript, since we have no data on long term outcome yet. Tobramycin and gentamicin: manuscript changed accordingly.