Late preterm: a new high risk group in neonatology

Late preterm infants are those infants born between 34 0/7 weeks through 36 6/7 week of gestation. These are physiologically less mature and have limited compensatory responses to the extrauterine environment compared with term infants. Despite their increased risk for morbidity and mortality, late preterm newborns are often cared in the well-baby nurseries of hospital after birth and are discharged from the hospital by 2-3 days of postnatal age. They are usually treated like developmentally mature term infants because many of them are of same birth weight and same size as term infants. There is a steady increase in the late preterm birth rate in last decade because of either maternal, fetal, or placental/uterine causes. There has been shift in the distribution of births from term and post-term toward earlier gestations. Although late preterm infants are the largest subgroup of preterm infants, there has been little research on this group until recently. This is mainly because of labeling them as "near-term". Such infants were being looked upon as "almost mature", and were thought as neonate requiring either no or minimal concern. In the obstetric and pediatric practice, late preterm infants are often considered functionally and developmentally mature and often managed by protocols developed for full-term infants. Thus, limited efforts are taken to prolong pregnancy in cases of preterm labor beyond 34 weeks, moreover after 34 weeks most centers do not administer antenatal prophylactic steroids. These practices are based on previous studies reporting neonatal mortality and morbidity in the late preterm period to be only slightly higher in comparison with term infants and whereas in the current scenario the difference is significant. Late preterm infants have 2-3-fold increased risk of morbidities such as hypothermia, hypoglycemia, delayed lung fluid clearance, respiratory distress, poor feeding, jaundice, sepsis, and readmission rates after initial hospital discharge. This leads to huge impact on the overall health care resources. In this review, we cover various aspects of these late preterm infants like etiology, immediate and long-term outcome.