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Limits of viability: definition of the gray zone
1Center for Fetal and Neonatal Medicine and the USC Division of Neonatal Medicine, Department of Pediatrics, Childrens Hospital Los Angeles, CA 90027, USA. iseri@chla.usc.edu
Insights
The limits of infant viability have shifted, with infants <23 weeks gestation or <500g generally not surviving intensive care. An algorithm is proposed for the uncertain
Area of Science:
- Neonatalogy
- Perinatal Medicine
- Developmental Pediatrics
Background:
- Improved survival and reduced long-term morbidity in very preterm infants have lowered the threshold for viability.
- Defining the limits of infant viability is crucial for guiding intensive care decisions.
Purpose of the Study:
- To review current literature on survival and neurodevelopmental outcomes in very preterm neonates.
- To establish current limits of infant viability and inform clinical decision-making.
Main Methods:
- Systematic review of published literature on very preterm infant survival and neurodevelopmental outcomes.
- Analysis of gestational age and birth weight thresholds for intensive care.
Main Results:
- Infants <23 weeks gestation or <500g have extremely low survival and acceptable neurodevelopmental outcomes.
- Infants ≥25 weeks gestation or ≥600g generally warrant intensive care, with >50% surviving without severe disability.
- Infants between 23-24 weeks gestation and 500-599g fall into a 'gray zone' with uncertain outcomes.
Conclusions:
- An algorithm is proposed for managing infants in the 'gray zone' of viability.
- Clinical application of the algorithm requires caution due to reliance on literature analysis and expert experience, not direct evidence.
Introduction:
As survival and long-term morbidity of very preterm infants have improved over the past decade, the limits of infant viability, the level of maturity below which survival and/or acceptable neurodevelopmental outcome are extremely unlikely, have also decreased.
Study Design:
In an effort to define the current limits of infant viability, the data in the literature on survival and long-term neurodevelopmental outcome in very preterm neonates have been reviewed.
Result:
The gestational age and birth weight below which infants are too immature to survive, and thus provision of intensive care is unreasonable, appears to be at <23 weeks and <500 g, respectively. Infants born at > or =25 weeks' gestation and with a birth weight of > or =600 g are mature enough to warrant initiation of intensive care, as the majority of these patients survive, and at least 50% do so without severe long-term disabilities. Finally, for infants born between 23(0/7) and 24(6/7) weeks' gestation and with a birth weight of 500 to 599 g, survival and outcome are extremely uncertain. For these infants born in the so-called 'gray zone' of infant viability, the line between patient autonomy and medical futility is blurred, and medical decision-making becomes even more complex and needs to embrace careful consideration of several factors. These factors include appraisal of prenatal data and the information obtained during consultations with the parents before delivery; evaluation of the patient's gestational age, birth weight and clinical condition upon delivery; ongoing reassessment of the patient's response to resuscitation and intensive care and continued involvement of the parents in the decision-making process after delivery.
Conclusion:
Based on these findings an algorithm is offered for consideration for neonatologists managing infants born in the 'gray zone' of infant viability. However, caution must be exercised when one considers incorporating this guideline into clinical practice because the algorithm is based on the analysis of the findings in the literature and the authors' experience rather than direct evidence.
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