peer reviewed ; Neonatal screening is becoming increasingly important in the spinal muscular atrophy (SMA) landscape. Yet there is a growing set of evidences that early pre-symptomatic management is much more efficient than post- symptomatic treatment, there is however no information available on the cost-effectiveness of SMA newborn screening (NBS). Such health economic analysis is nevertheless very important to convince policy makers to allocate funds for NBS. We will present the health-economic data of pre-symptomatic and post-symptomatic treated patients in Belgium that will further be used to assess the cost-effectiveness of NBS. Between March 2018 and February 2020, screening was conducted among 71,000 newborns, among which 9 were detected with SMA. All but one identified patients were treated before the onset of symptoms: 5 with nusinersen (one was mildly symptomatic at the time of treatment), 2 with Zolgensma, 1 with Risdiplam and the last one to be determined. Survival, costs and quality of life of these 9 patients (aged between 10 days and 18 months) are currently prospectively collected. In addition, data from 3 additional asymptomatic patients who were siblings of affected children are also collected. Survival, health care resources consumption and quality of life data have also been collected on symptomatic treated and untreated patients. For untreated patients, we collected prospectively the data during two years in 81 patients (53 patients with SMA Type 2, 9 non-ambulant with SMA Type 3 and 19 ambulant with SMA Type 3). We are also collecting similar data prospectively in 30 symptomatic patients treated with nusinersen and 2 untreated patients, aged between 4 months and 60 years (9 patients with SMA 1, 14 patients with SMA 2, and 9 patients with SMA 3). Two-thirds of these patients already have at least 2 years of follow-up. Using these three sets of data, we are currently developing a model to assess the cost-effectiveness of newborn screening for SMA. We will present the preliminary results ...