The goal of this study is to develop a new scale for assessing prolonged pain, dedicated to extremely premature infants born before 27 weeks of gestation, adapted to their particular ways of expressing pain and discomfort, which will be called the EDEX (Extremely Premature Infant Pain Assessment Scale).

This scale will take into account the level of development of extremely premature infants, recognizing that the perception and manifestations of pain vary according to gestational age.

It was chosen to develop a specific pain assessment scale for preterm infants born before 27 weeks of gestation, in line with their level of development and their relatively homogeneous manifestations in this population.

This population, which is the most immature, is particularly fragile and sensitive to its environment and the care provided. Pain manifestations are the most subtle, vegetative reactions are very present, and the motor system is still underdeveloped, linked to low muscle tone.

It is with this category of patients that the nursing staff encounter the most difficulty in assessing pain and discomfort based on the EDIN scale.

After creating the new EDEX scale during the first phase of the DOU-PREMA study, both scales (EDIN and EDEX) will be administered to the same pool of extremely premature infants during the second phase of the DOU-PRÉMA study in order to assess the correlation between the two scales.

The main hypothesis is that EDIN and EDEX scores will not be correlated, as the EDIN does not appear to be suitable for extremely premature infants in routine practice.

if the hypothesis is confirmed, a multicenter psychometric validation of the EDEX scale will then be considered in a future study.

The study is a monocentric, non-interventional observational study conducted in the neonatal intensive care unit (NICU) of the University Hospital of Reunion Island (Site Nord). It is designed as a preliminary step toward the psychometric validation of a newly developed behavioral pain and discomfort assessment scale for extremely preterm infants (<27 weeks' gestational age), named EDEX.

The study includes two sequential phases:

1. a developmental phase dedicated to the creation of the EDEX scale : This stage is based on the production of videos of premature extreme in order to ajust the provisional scale define during a multidisciplinary meeting.
2. a cross-sectional observational phase comparing EDEX with the EDIN scale in the same population.

The second phase of the project will evaluate the correlation between EDIN and EDEX scores.

This protocol follows the SPIRIT recommendations for study protocols involving human participants.

Inclusion Criteria:

Extremely premature infants:

• born before 27 weeks of gestation, and aged no more than 26 weeks of amenorrhea + 6 days in corrected age,
• from 48 hours of life,
• hospitalised in neonatal intensive care,
• for whom at least one of the two legal guardians has given their consent.

Exclusion Criteria:

Extreme premature infants:

• whose clinical condition is critical with a risk of imminent death,
• with major brain damage (HIV 4) or major brain malformations,
• deeply sedated or paralyzed with no spontaneous reactions,
• whose parents are both minors.
• who are not already participating in another study.

Extremely premature infants(< 27 weeks of amenorrhea) hospitalised in neonatal intensive care at University Hospital Centre of Reunion Island