Short-term outcomes of infants born at 35 and 36 weeks gestation: we need to ask more questions.

BACKGROUND: Newborns who are 35 to 36 weeks gestation comprise 7.0% of all live births and 58.3% of all premature infants in the United States. They have been studied much less than very low birth weight infants.

OBJECTIVE: To examine available data permitting quantification of short-term hospital outcomes among infants born at 35 and 36 weeks gestation.

DESIGN: Review of existing published data and, where possible, re-analysis of existing databases or retrospective cohort analyses.

SETTING: Multiple hospitals and neonatal intensive care units in the United States and England.

PATIENTS: Premature infant cohorts with infants whose dates of birth ranged from 1/1/98 through 6/30/04.

MAIN OUTCOME MEASURES: 1) Death, 2) respiratory distress requiring some degree of in-hospital respiratory support during the birth hospitalization, and 3) rehospitalization following discharge home after the birth hospitalization.

RESULTS: Newborns born at 35 and 36 weeks gestation experienced considerable mortality and morbidity. Approximately 8% required supplemental oxygen support for at least 1 hour, almost 3 times the rate found in infants born at > or =37 weeks. Among 35 to 36 week newborns who progressed to respiratory failure and who survived to 6 hours of age and did not have major congenital anomalies, the mortality rate was 0.8%. Following discharge from the birth hospitalization, 35 to 36 week infants were much more likely to be rehospitalized than term infants, and this increase was evident both within 14 days as well as within 15 to 182 days after discharge. In addition, late preterm infants experienced multiple therapies, few of which have been formally evaluated for safety or efficacy in this gestational age group.

CONCLUSIONS: Greater attention needs to be paid to the management of late preterm infants. In addition, it is important to conduct formal evaluations of the therapies and follow-up strategies employed in caring for these infants.