Analysis of neonatal morbidity and mortality in late-preterm newborn infants.

Objective: To compare mortality and the principal intercurrent clinical conditions suffered by late-preterm newborn infants born with gestational ages of 34 full weeks to 36 weeks and 6 days, and full term newborns.

Methods: This was a cross-sectional study of all preterm newborn infants born at a public hospital from August 2010 to August 2011. The study sample comprised late-preterm infants (cases) and a group of full term newborns (controls). Three controls were enrolled for each case. Maternal, gestational and neonatal variables were analyzed. Means and standard deviations were used to compare numerical variables between case and control groups using Student's t test and the Mann-Whitney test; Pearson's chi-square was used for categorical variables. Odds ratios and 95% confidence intervals were calculated to estimate risk.

Results: The study sample comprised 239 late-preterm infants and 698 full term newborns. Mothers aged over 35 years and/or with a history of previous premature deliveries had a higher proportion of late-preterm children. The following gestational variables were associated with late-preterm delivery: hypertension, infectious diseases, rupture of membranes more than 18 hours previously and multiple pregnancies. When compared with full term newborns, late-preterms were statistically more likely to be subject to hypothermia/hyperthermia, hypoglycemia, respiratory pathologies, resuscitation in the delivery room, phototherapy, supplementary feeding, mechanical ventilation, venous infusions, antibiotics and admission to the neonatal intensive care unit, resulting in a nine times greater neonatal mortality rate. Intercurrent conditions were inversely related to gestational age.

Conclusion: Late-preterm newborn infants had a mortality rate nine times that of full term infants and were exposed to a greater risk of intercurrent conditions during the neonatal period. These intercurrent conditions were inversely related to gestational age.