[Late preterm infants: A population at underestimated risk]

There has been a gradual rise in prematurity rates recent years, almost exclusively at the expense of the late preterm (34 to 36 weeks). This population, although with less risk than smaller preterm gestational age, has a morbidity rate significantly higher than term infants. However, there is some underestimation regarding developments in the short and long term. The aim of this study was to look at the incidence of prematurity in our institution and to analyze morbidity and mortality in late preterm compared with term infants

We performed a retrospective review of newborns in our Hospital from January 1992 until December 31, 2008. Late preterm group was defined as between 34(0/7) and 36(6/7) weeks gestation (N=2003) and term infants from 37 to 42 weeks gestation (N=32015). We formed 2 subgroups according two time periods (1992-1998 and 2000-2008). The morbidity and mortality for each of the groups and subgroups, and the morbidity from week 34 to 42, were analysed and compared.

During the period studied, the prematurity rate increased from 3.9% to 9.8%, exclusively at the expense of the late preterm (79%). The rate of mortality in late preterm was 5 per thousand compared to 1.1 per thousand in the term (P <0.0001, OR 4.71, 95% CI 2.3-9.5). The incidence of admission to the Neonatal Unit, Cesarean rate, twin, respiratory disorders, need for respiratory support in the form of nasal CPAP or mechanical ventilation, incidence of apnea, jaundice requiring phototherapy, hypoglycaemia and need for parenteral nutrition were significantly higher (P<0.0001) in the late preterm group compared with term infants. The morbidity rate decreased significantly as gestational age increased, with the lowest value from 39 weeks.

Morbidity and mortality in late preterm infants is significantly higher than in term infants. The guidelines for these near term premature babies need to be reviewed, looking for possible causes of prematurity, and trying to reduce their impact, as well as developing a protocol for their care and close monitoring to minimize the associated morbidity. There should be long-term monitoring to find out the consequences on their psychomotor development. The obstetrics group should be made aware of the true risks of births in the near-term gestational ages.