Elsevier

Seminars in Perinatology

Volume 30, Issue 1, February 2006, Pages 28-33
Seminars in Perinatology

Short-Term Outcomes of Infants Born at 35 and 36 Weeks Gestation: We Need to Ask More Questions

Presented at four platform sessions on July 18 and 19, 2005, at a conference sponsored by the National Institute for Child Health and Human Development, in Bethesda, Maryland.
https://doi.org/10.1053/j.semperi.2006.01.005Get rights and content

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 ≥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.

Section snippets

Study Populations

Our study populations consist of cohorts of late preterm infants as reported in recent studies. We restricted ourselves to those studies that (1) did not limit reporting of premature infant outcomes to a single gestational age category (<37 weeks) and (2) permitted some inference as to the outcomes experienced by babies ≥34 weeks gestation. We were also able to re-analyze data from a recently published study12 so as to isolate the outcomes of late preterm infants. Lastly, we conducted some

Respiratory Distress

The most comprehensive analyses of the epidemiology of respiratory distress are the geographically based studies in Sweden, which reported on babies born in the late 1970s16, 17, 18 and Italy, which reported on babies born in the mid 1990s.19, 20, 21 Both groups of studies found that the rate of occurrence of any form of respiratory distress increased dramatically among babies born at less than 37 weeks. The results reported by these studies are similar to those found in the analysis of the

Discussion

It is clear from both the limited literature base as well as from our exploratory analyses that late preterm infants, however defined, experience greater mortality and morbidity than term infants. In the immediate neonatal period, one of the major drivers for increased mortality and morbidity is the presence of various forms of respiratory distress, of which the most common forms are respiratory distress syndrome, pneumonia, and a variety of ill-defined conditions usually lumped under the

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