•Congenital myotonic dystrophy type 1 (CMD1) is a rare neuromuscular disease.•CDM1 is characterized by neonatal hypotonia, weakness, feeding and respiratory difficulties.•Many CMD1 patients suffer from hypoxic ischemic encephalopathy (HIE).•HIE, preterm delivery, resuscitation and hypothermia treatment are poor prognostic factors for survival.•Respiratory insufficiency is the main life-threatening factor in CDM1. Congenital myotonic dystrophy type 1 (CDM1) is a rare neuromuscular disease. The aim of our study was to evaluate clinical variability of CDM1 and factors that may influence survival in CDM1. Research included 24 pediatric patients with CDM1. Most of our patients had some form of hypoxic ischemic encephalopathy (HIE) (74 %), from mild to severe. Prolonged and complicated deliveries (75 %), high percentage of children resuscitated at birth (57 %) and respiratory insufficiency (46 %) with consequent hypoxia were the main reasons that could explain high percentage of HIE. Therapeutic hypothermia was applied in three children with poor outcome. Median survival of all CDM1 was 14.2 ± 1.5 years. Six patients had a fatal outcome (25 %). Their mean age of death was 3.0 ± 2.8 years. Poor prognostic factors for the survival of our CDM1 patients were: preterm delivery, resuscitation at birth, severe HIE, hypothermia treatment and permanent mechanical ventilation. Respiratory insufficiency was the main life-threatening factor. Our data clearly indicates the need to develop natural history studies in CDM1 in order to enhance the standards of care and to develop clinical trials investigating causative therapies in pediatric patients with CDM1.