[Epidemiology of preterm birth: Prevalence, recent trends, short- and long-term outcomes].

Every year, approximately 15 million babies are born preterm worldwide (before 37 completed weeks of gestation), putting the global preterm birth rate at 11%; they are about 60,000 in France. About 85% of these births are moderate (32-33 weeks) to late preterm babies (34-36 weeks), 10% are very preterm babies (28-31 weeks) and 5% are extremely preterm babies (< 28 weeks). Though neonatal mortality rates are dropping, they remain high and are largely determined by gestational age at birth (over 10% mortality for infants born before 28 weeks, 5-10% at 28-31 weeks and 1-2% at 32-34 weeks). Severe neonatal morbidity and disabilities during childhood are also frequent and vary with gestational age. For example, the risk of motor or cognitive impairment is 2 to 3 times higher among children born between 34 and 36 weeks than among children born full-term. Therefore, every preterm baby must be carefully monitored. Recent cohort studies have focused on extremely preterm births; however, awareness of potential outcome and prognosis of all preterm babies is a crucial step for health professionals caring for these children. Huge disparities exist between high- and low-income countries, but also among high-income countries themselves.