Although significant advances in neonatal care have increased survival rates of preterm infants born before 28 weeks gestation, a concomitant decrease in neuro developmental disorders has not been achieved. Cerebral injuries, well documented during the previous years, in preterm babies are particularly deleterious since they occur in a developing brain. They affect both white and grey matter by complex mechanisms and the principal targets are the developing oligodendrocytes and neurons of the subplate. All these criteria define the encephalopathy of prematurity. Nevertheless, the consequences of prematurity at the level of the brainstem are not very well known and may explain neuro-developmental disorders with normal MRI.

The assessment of the motor repertoire is complementary to the neurological examination and may represent a diagnostic tool for cerebral palsy, mild motor deficits and delayed acquisition in children. The newborn have a rich motor repertoire. GMs play a key role in the development due to the feedback that they send to cortical neurons and reflect the maturational stage of the Central Nervous System (CNS). Lesions of the brainstem caused by prematurity may induce alterations of the motor repertoire.

Dysautonomic disorders, such as bradycardia, apneas, feeding problems, that occur frequently in very preterm babies reflect brainstem abnormalities. These symptoms are also described in other pathologies, in Rett syndrome and sudden infant death syndrome (SIDS). In these pathologies deficits of the 5-HT system have been described and associated with dysautonomia. It would then be interesting to evaluate 5-hydroxytryptamine (5-HT) levels in very preterm babies.

The serotonergic system develops very early during gestation and is one of the first neurotransmitter to appear in the developing brain. The main 5-HT nuclei are located within the brainstem. 5-HT plays an important role in the homeostasis and the modulation of the respiratory network. Moreover, previous studies have shown that 5-HT projections to the spinal cord are involved in posture and in the coordination. It is tempting to think that 5-HT deficits may have some repercussions on the development of the CNS, changing activity dependent processes, such as spontaneous activity recorded at the spinal level in rodents.

In this project, the 5-HT platelet levels in preterm infants born before 28 weeks will be compared with newborns. a correlation between the levels of 5-HT with MRI of the posterior fossa, GMs and dysautonomia different parameters such as heart rate variability, suction-swallowing and different breathing techniques will be established

Inclusion Criteria:

• Birth less than 28 weeks
• known gestational age
• Birth in born
• Infant without genetic syndrom, evolutive neurologic disease, chronic disorder, malformative pathology
• Infant without intra-ventricular haemorrhage with dilatation or intraparenchymal haemorrhage
• Infants without mechanical ventilation

Exclusion Criteria:

• Infant with congenital cardiopathy, congenital brainstem disorder, Pierre Robin sequence