Smarter Decisions,
Better Care

UpToDate synthesizes the most recent medical information into evidence-based practical recommendations clinicians trust to make the right point of care decisions.

  • Rigorous editorial process: Evidence-based treatment recommendations
  • World-Renowned physician authors: over 5,100 physician authors around the globe
  • Innovative technology: integrates into the workflow; access from EMRs

For more information, click below.


Subscribers log in here


Limit of viability

INTRODUCTION

The limit of viability is defined as the stage of fetal maturity that ensures a reasonable chance of extrauterine survival. Determining the limit of viability is desirable so that interventions that are costly and painful can be avoided in the infant who does not have a chance of survival [1]. However, deciding upon a threshold of viability is challenging because it remains uncertain which extremely preterm infants have a reasonable chance of survival [2-4].

Survival and morbidity of extremely premature infants born below 26 weeks gestation will be reviewed here. In addition, a management approach for infants born at the limit of viability based upon prognosis will be presented.

SURVIVAL RATES

Factors that affect survival rates in extremely premature infants (gestational age <26 weeks) include gestational age, birth weight, gender, plurality, and the use of antenatal corticosteroid therapy [3,5,6].

Gestational age — The major factor in determining viability is gestational age. Survival rates reported in eight studies [2,3,7-13] during the initial NICU admission for infants 22 to 25 completed weeks gestation (220/7 to 256/7 weeks gestation) are displayed in the table (table 1). These reports span time periods ranging from six months to six years between 1994 and 2010, and represent several large geographic areas in Western Europe, Japan, and a network of tertiary level academic centers in the United States. These data clearly demonstrated the rise of survival rate as gestational age increased from 22 to 25 weeks. In addition, they also showed improved survival, as survival rates increased significantly for infants born at 23 to 25 weeks gestation. However, it remains uncertain whether the survival rates for infants born at 22 weeks gestation have improved over time.

These data emphasize the importance of basing discussions about delivery room management for infants at borderline viability upon the latest available data. In addition, although these results highlight the impact of gestational age on viability, it is important to recognize that ascertaining an accurate gestational age is challenging. Thus, reliance on estimated gestational age may not truly reflect the prognosis. (See 'Interpreting the data' below and "Postnatal assessment of gestational age" and "Prenatal assessment of gestational age".)

                

Subscribers log in here

To continue reading this article you must have access through your hospital or your group practice, log in to your personal subscription, or purchase a personal subscription. For more information, click below.
Literature review current through: May 2013. | This topic last updated: Feb 12, 2013.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2013 UpToDate, Inc.
References
Top
  1. Batton DG, Committee on Fetus and Newborn. Clinical report--Antenatal counseling regarding resuscitation at an extremely low gestational age. Pediatrics 2009; 124:422.
  2. Field DJ, Dorling JS, Manktelow BN, Draper ES. Survival of extremely premature babies in a geographically defined population: prospective cohort study of 1994-9 compared with 2000-5. BMJ 2008; 336:1221.
  3. Tyson JE, Parikh NA, Langer J, et al. Intensive care for extreme prematurity--moving beyond gestational age. N Engl J Med 2008; 358:1672.
  4. Seri I, Evans J. Limits of viability: definition of the gray zone. J Perinatol 2008; 28 Suppl 1:S4.
  5. Modi N. Survival after extremely preterm birth. BMJ 2008; 336:1199.
  6. Bader D, Kugelman A, Boyko V, et al. Risk factors and estimation tool for death among extremely premature infants: a national study. Pediatrics 2010; 125:696.
  7. Costeloe K, Hennessy E, Gibson AT, et al. The EPICure study: outcomes to discharge from hospital for infants born at the threshold of viability. Pediatrics 2000; 106:659.
  8. Larroque B, Bréart G, Kaminski M, et al. Survival of very preterm infants: Epipage, a population based cohort study. Arch Dis Child Fetal Neonatal Ed 2004; 89:F139.
  9. Markestad T, Kaaresen PI, Rønnestad A, et al. Early death, morbidity, and need of treatment among extremely premature infants. Pediatrics 2005; 115:1289.
  10. Itabashi K, Horiuchi T, Kusuda S, et al. Mortality rates for extremely low birth weight infants born in Japan in 2005. Pediatrics 2009; 123:445.
  11. EXPRESS Group, Fellman V, Hellström-Westas L, et al. One-year survival of extremely preterm infants after active perinatal care in Sweden. JAMA 2009; 301:2225.
  12. Stoll BJ, Hansen NI, Bell EF, et al. Neonatal outcomes of extremely preterm infants from the NICHD Neonatal Research Network. Pediatrics 2010; 126:443.
  13. Seaton SE, King S, Manktelow BN, et al. Babies born at the threshold of viability: changes in survival and workload over 20 years. Arch Dis Child Fetal Neonatal Ed 2013; 98:F15.
  14. Kugelman A, Bader D, Lerner-Geva L, et al. Poor outcomes at discharge among extremely premature infants: a national population-based study. Arch Pediatr Adolesc Med 2012; 166:543.
  15. Manktelow BN, Seaton SE, Field DJ, Draper ES. Population-based estimates of in-unit survival for very preterm infants. Pediatrics 2013; 131:e425.
  16. Bodeau-Livinec F, Marlow N, Ancel PY, et al. Impact of intensive care practices on short-term and long-term outcomes for extremely preterm infants: comparison between the British Isles and France. Pediatrics 2008; 122:e1014.
  17. Hintz SR, Kendrick DE, Wilson-Costello DE, et al. Early-childhood neurodevelopmental outcomes are not improving for infants born at <25 weeks' gestational age. Pediatrics 2011; 127:62.
  18. Guinsburg R, Branco de Almeida MF, Dos Santos Rodrigues Sadeck L, et al. Proactive management of extreme prematurity: disagreement between obstetricians and neonatologists. J Perinatol 2012; 32:913.
  19. Donovan EF, Tyson JE, Ehrenkranz RA, et al. Inaccuracy of Ballard scores before 28 weeks' gestation. National Institute of Child Health and Human Development Neonatal Research Network. J Pediatr 1999; 135:147.
  20. Mercurio MR. The ethics of newborn resuscitation. Semin Perinatol 2009; 33:354.
  21. Batton DG, DeWitte DB, Pryce CJ. One hundred consecutive infants born at 23 weeks and resuscitated. Am J Perinatol 2011; 28:299.
  22. Carlo WA, McDonald SA, Fanaroff AA, et al. Association of antenatal corticosteroids with mortality and neurodevelopmental outcomes among infants born at 22 to 25 weeks' gestation. JAMA 2011; 306:2348.
  23. Smith PB, Ambalavanan N, Li L, et al. Approach to infants born at 22 to 24 weeks' gestation: relationship to outcomes of more-mature infants. Pediatrics 2012; 129:e1508.
  24. Roberts G, Anderson PJ, Doyle LW, Victorian Infant Collaborative Study Group. The stability of the diagnosis of developmental disability between ages 2 and 8 in a geographic cohort of very preterm children born in 1997. Arch Dis Child 2010; 95:786.
  25. Marlow N, Wolke D, Bracewell MA, et al. Neurologic and developmental disability at six years of age after extremely preterm birth. N Engl J Med 2005; 352:9.
  26. Mercurio MR. Physicians' refusal to resuscitate at borderline gestational age. J Perinatol 2005; 25:685.
  27. Mercurio MR. Parental authority, patient's best interest and refusal of resuscitation at borderline gestational age. J Perinatol 2006; 26:452.
  28. Wellesley H, Jenkins IA. Withholding and withdrawing life-sustaining treatment in children. Paediatr Anaesth 2009; 19:972.
  29. American Heart Association and American Academy of Pediatrics. Neonatal Resuscitation, 6th ed, Kattwinkel J (Ed), American Academy of Pediatrics, Elk Grove Village 2011. p.5.
  30. Kattwinkel J, Perlman JM, Aziz K, et al. Neonatal resuscitation: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Pediatrics 2010; 126:e1400.
  31. D'Angio CT, Mercurio MR. Evidence-based ethics in the 'gray zone' of neonatal viability: promises and limitations. Pediatr Health 2008; 2:777.
  32. Nuffield Council on Bioethics. Guidelines on giving intensive care to premature babies. 2006. http://www.nuffieldbioethics.org/neonatal-medicine/neonatal-medicine-background-extremely-premature-babies (Accessed on February 07, 2011).