Technical advances in genome sequencing are removing barriers to identifying disease-causing genetic variants in clinical care and population health. The use of genomic sequencing as a complement to existing newborn screening is gaining interest in many countries. However, this development pushes us to assess rationales for what we screen for and why. The inclusion of adult-onset or untreatable conditions in gene lists for genomic newborn screening is a key issue to consider when designing such programs. Internationally recognised screening principles would not condone reporting these conditions. However, some argue it is ethically acceptable and certain programs do include these conditions. In this paper, we examine whether reporting findings related to adult-onset or untreatable conditions in population-based genomic newborn screening programs is ethically justifiable. We argue that there should be a presumption against reporting them, as this practice risks undermining core public health rationales of screening. It also infringes on a child’s future autonomy and may create “patients-in-waiting”. While the interests of other family members and the avoidance of mis-diagnosis or long lead times to diagnosis are important, they should not override core aims of newborn screening. Moreover, a practice of reporting adult-onset or untreatable conditions may strain health system resources and exacerbate inequities. While offering information is alluring, genomic newborn screening must remain anchored in population screening principles. As such, adult-onset or untreatable conditions should not, in principle, be reported. While genomics offers significant promise for newborn screening, it must not be used to shift programs towards more speculative benefits.