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Original Investigation
March 25, 2019

Outcomes of Extremely Preterm Infants With Birth Weight Less Than 400 g

Author Affiliations
  • 1Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
  • 2Social, Statistical, and Environmental Sciences Unit, RTI International, Research Triangle Park, North Carolina
  • 3Department of Pediatrics, University of Iowa, Iowa City
  • 4Department of Pediatrics, University of Alabama at Birmingham
  • 5Department of Pediatrics, Stanford University, Palo Alto, California
  • 6Department of Pediatrics, Brown University, Providence, Rhode Island
  • 7Department of Pediatrics, University of Texas Health Science Center at Houston
  • 8Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas
  • 9Children’s Health Research Center, Sanford Research, Sioux Falls, South Dakota
  • 10Department of Pediatrics, University of Pennsylvania, Philadelphia
  • 11Social, Statistical, and Environmental Sciences Unit, RTI International, Rockville, Maryland
  • 12Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
JAMA Pediatr. 2019;173(5):434-445. doi:10.1001/jamapediatrics.2019.0180
Key Points

Question  What are the mortality and morbidity risks for infants with a birth weight less than 400 g?

Findings  In this cohort study of 205 inborn, preterm infants with a birth weight less than 400 g and a gestational age of 22 to 26 weeks, 26 liveborn infants (12.7% of liveborn infants; 25.7% of those actively treated at birth) survived to discharge. Among the 19 infants in the 2008 to 2015 birth cohort who completed follow-up evaluation (10% of liveborn infants; 21% of actively treated infants), 14 (74%) had neurodevelopmental impairment.

Meaning  Infants with a birth weight less than 400 g are at risk of significant, but not universal, morbidity and mortality.

Abstract

Importance  Birth weight (BW) is an important predictor of mortality and morbidity. At extremely early gestational ages (GAs), BW may influence decisions regarding initiation of resuscitation.

Objective  To characterize outcomes of liveborn infants with a BW less than 400 g.

Design, Setting, and Participants  This retrospective multicenter cohort study analyzed extremely preterm infants born between January 2008 and December 2016 within the National Institute of Child Health and Human Development Neonatal Research Network. Infants with a BW less than 400 g and a GA of 22 to 26 weeks were included. Active treatment was defined as the provision of any potentially lifesaving intervention after birth. Survival was analyzed for the entire cohort; neurodevelopmental impairment (NDI) was examined for those born between January 2008 and December 2015 (birth years with outcomes available for analysis). Neurodevelopmental impairment at 18 to 26 months’ corrected age (CA) was defined as a Bayley Scales of Infant and Toddler Development, Third Edition, cognitive composite score less than 85, a motor composite score less than 85, moderate or severe cerebral palsy, gross motor function classification system score of 2 or greater, bilateral blindness, and/or hearing impairment. Data were analyzed from September 2017 to October 2018.

Exposures  Birth weight less than 400 g.

Main Outcomes and Measures  The primary outcome was survival to discharge among infants who received active treatment. Analysis of follow-up data was limited to infants born from 2008 to 2015 to ensure children had reached assessment age. Within this cohort, neurodevelopmental outcomes were assessed for infants who survived to 18 to 26 months’ CA and returned for a comprehensive visit.

Results  Of the 205 included infants, 121 (59.0%) were female, 133 (64.9%) were singletons, and 178 (86.8%) were small for gestational age. Almost half (101 of 205 [49.3%]) received active treatment at birth. A total of 26 of 205 infants (12.7%; 95% CI, 8.5-18.9) overall survived to discharge, and 26 of 101 actively treated infants (25.7%; 95% CI, 17.6-35.4) survived to discharge. Within the subset of infants with a BW less than 400 g and a GA of 22 to 23 weeks, 6 of 36 actively treated infants (17%; 95% CI, 6-33) survived to discharge. Among infants born between 2008 and 2015, 23 of 90 actively treated infants (26%; 95% CI, 17-36) survived to discharge. Two infants died after discharge, and 2 were lost to follow-up. Thus, 19 of 90 actively treated infants (21%; 95% CI, 13-31) were evaluated at 18 to 26 months’ CA. Moderate or severe NDI occurred in 14 of 19 infants (74%).

Conclusions and Relevance  Infants born with a BW less than 400 g are at high risk of mortality and significant morbidity. Although 21% of infants survived to 18 to 26 months’ CA with active treatment, NDI was common among survivors.

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