New molecular therapies are available for the treatment of spinal muscular atrophy (SMA) but early intervention is required. We report two cases that were diagnosed prenatally, where treatment with nusinersen was initiated within 7 h and three days respectively. The children were followed up for 13 months and almost six years respectively. Both children have developed within entirely normal centiles, indicating that initiating treatment immediately after birth, as in these cases, is essential for a good outcome.