Advancements in perinatal care have significantly improved the survival of extremely premature infants, establishing a viability threshold below 25 weeks' gestational age (GA). However, management at the limit of viability poses ethical and decision-making problems for health-care professionals. They grapple with the delicate balance between potential survival and long-term disabilities.

These decisions, as well as the information given to families, are based on knowledge of the prognosis as assessed by national and international epidemiological studies. Healthcare professionals rely on population-based estimations but face discrepancies in predicting outcomes because there are significant variation depending on perinatal center and country where infants are hospitalized. In the large French epidemiological study, 9,6% of livebirths included were born at 22-25 wks and only 38% survived.

In the neonatology department of the croix rousse, these infants have been actively cared for for many years, which has allowed the development of specific skills that are essential for the proper management of these very high-risk patients. Furthermore, EPIPAGE 2 included data from centers where perinatal management was probably not very active at these extreme ages. It results in worse neonatal outcomes as evaluated at the national level than outcomes data evaluated at the neonatal intensive care unit of Croix-Rousse hospital. Using data from EPIPAGE 2 study for clinical decision could lead to avoid active care at the for some infants at the limit of viability It is needed to obtain complete evaluation of neonatal outcomes of infants hospitalized at the Croix-Rousse hospital, so that clinicians may rely on actualized data related to the practices in their perinatal center. It is also needed to compare outcomes with data from large national and international cohorts, to identify and quantify differences. Data about later neurodevelopment outcomes, at 2 years, are also needed as it can taken in consideration in decision-making process.

Inclusion Criteria:

• Infants born between 22 and 25 weeks gestational age
• Infants hospitalized at the tertiary care neonatal unit of Croix-Rousse hospital
• Infants born between January 2010 and December 2019

Exclusion Criteria:

- None

Extremely premature newborn (between 22 and 25 weeks gestational age) treated at the Croix-Rousse hospital