Mortality and Morbidity Data for Infants with Extremely Low Birthweights (ELBW)

The data presented in this section of the NRP website are intended to serve as reference material for Chapter 9 of the NRP Textbook, Edition 5. They are not intended to reflect exact current outcome data in your hospital or your perinatal region. However, the NRP Steering Committee believes that these data are sufficiently representative of ELBW outcome to help the practitioner when counseling parents about resuscitation options at the margin of viability. It is very important that these data be considered in combination with local and regional statistics that may better reflect available resources and care practices. Although the NRP is designed for health care practitioners who practice in the United States, we have included some data collected in other developed countries, because in some cases these represented a more comprehensive data set.

The following additional caveats should be considered when interpreting the data:

  • Most of the studies reported data only for babies who were born alive; further, some studies only report outcomes for those babies who were resuscitated and admitted to neonatal units.
  • Institutional definitions of "born alive" may have varied among the studies, and there were likely inconsistencies in the aggressiveness with which babies with estimated gestational ages <26 weeks were resuscitated in the different study populations.
  • Much of the mortality data and all of the morbidity data are derived from babies who were born over a decade ago, when the techniques, resources, and philosophy concerning resuscitation and management of ELBW babies were different than they are today.
  • Most of the studies reflect data from babies born in facilities with comprehensive resuscitation resources and personnel who had been recently trained in optimum resuscitation techniques.

The represented datasets were reported in the following publications:

  1. Costeloe K, Hennessy E, Gibson AT, Marlow N et al. The EPICure study: outcomes to discharge from hospital for infants born at the threshold of viability. Pediatrics 2000, 106: 659-671.
  2. Lemons J, Bauer C, Oh W, Korones S, et al. Very low birth weight outcomes of the National Institute of Child Health and Human Development Neonatal Research Network, January 1995 through December 1996. Pediatrics 2001, 107:e1-e8.
  3. Markestad T, Kaaresen PI, Ronnestad A, Reigstad H, Lossius K et al. Early death, morbidity and need of treatment among extremely premature infants. Pediatrics 2005, 115: 1289-98.
  4. Finer N, Horbar JD, Carpenter JH for the Vermont Oxford Network. Cardiopulmonary resuscitation in the very low birthweight infant. The Vermont Oxford experience. Pediatrics 1999; 104: 428-34.
  5. National Center for Health Statistics, 2001.
  6. Vohr B, Wright L, Poole W, and McDonald S. Neurodevelopmental outcomes of extremely low birth weight infants <32 weeks’ gestation between 1993 and 1998.
  7. Wood N, Marlow N, Costeloe K, Gibson A, and Wilkinson A. Neurologic and developmental disability after extremely preterm birth. New Engl J Med 2000, 343:378-84.
  8. Marlow N, Wolke D, Bracewell MA, Samara M; EPICure Study Group. Neurologic and developmental disability at 6 years of age after extremely preterm birth. N Engl J Med 2005, 352: 9-19.
  9. Unpublished data provided courtesy of the Vermont Oxford Network.
  10. Tyson JE, Parikh NA, Langer J, Green C, and Higgins RD. Intensive care for extreme prematurity—Moving beyond gestational age. N Engl J Med 2008, 358:1672-81.

*The complete text of reference #10 can be accessed at, or you can download the pdf of the original article. Additional information on survival rates based on the combination of gestational age and birthweight, as well as other factors that have been shown to affect outcomes, can be found in the Supplementary Materials for reference #10 that can be accessed on the Web at

Table 1. Survival rates by gestational age for infants ≤25 weeks EGA

Population Birth year(s) 22 weeks 23 weeks 24 weeks 25 weeks Comments
UK and Republic of Ireland1 1995 2%/ 9%
(n=138/ 22)
22%/ 20%
(n=241/ 131)
26%/ 34%
(n=382/ 298)
44%/ 52%
(n=424/ 357)
All liveborn/ NICU admissions
NICHD Network centers2 1995 & 1996 21%
All liveborn infants; infants w/ congenital malformations excluded
Norway3 1999 & 2000 5%/ 0%
(n=38/ 0)
16%/ 39%
(n=55/ 23)
44%/ 60%
(n=80/ 58)
66%/ 80%
(n=83/ 69)
All deliveries/ NICU admissions
NICHD Network centers10 1998-2003 5% 26% 56% 75% 4,466 inborn infants at 19 centers; excludes infants w/ BW >1000 g or who did not require mechanical ventilation
Vermont-Oxford Network centers9 2003-2005 5% (n=2,625) 29% (n=5,481) 56% (n=8,722) 73% (n=9,795) All infants born at a member hospital or transferred to a member hospital at ≤ 28 days postnatal age

Table 2. Survival rates by birth weight for infants ≤1000g

Population origin Birth Year(s) <500g 500-750g 750-1000g Comments
UK and Republic of Ireland1 1995 6% (n=33) 32% (n=497) 56% (n=276) NICU admissions
Network centers2
1995-1996 11% 52% (500-800g) 85% All liveborn infants; infants w/ congenital malformations excluded
Vermont - Oxford Network units4 1994-1996 17% (n=497) 60% (n=5334) 90% (n=6336) All liveborn; lethal anomlies excluded
Norway3 1999 & 2000 10% / 54%
(n=71/ 13)
42% / 68%
(n=216/ 92)
78% / 88%
(n= 268/ 240)
All deliveries/ NICU admissions
United States5 2001 14% (n=6450) 52% (n=11,081) 85% (n=11,847) All live births
Vermont-Oxford Network centers9 2003-2005 17% (n=4,662) 56% (n=22,649) 85% (n=27,052) All infants born at a member hospital or transferred to a member hospital at ≤ 28 days postnatal age
NICHD Network centers2
(100g increments)
29% (n=317)
64% (n=449)
74% (n=439)
86% (n=419)
90% (n=462)
All liveborn infants; infants w/ congenital malformations excluded

Table 3. Survival rates by gestational age, gender, and birthweight for infants ≤25 weeks EGA and ≤600 g10

Birthweight 22 weeks 23 weeks 24 weeks
Male Female Male Female Male Female
401g-500g 3% 2% 8% 19% 26% 28%
501g-600g 6% 9% 21% 21% 35% 49%