SCIENCE
ABORTION
Defining Viability
In medicine, viability refers to the stage at which a fetus can survive outside the womb with medical support. It is not a fixed biological event, but a clinical judgment influenced by gestational age, physiological development, and available technology. The Royal College of Obstetricians and Gynaecologists explains that “viability is dependent upon gestational age, fetal development, and the level of neonatal care available,” and therefore “cannot be defined by a single universal gestational age.” ( 1 )
Medical authorities caution against equating viability with the beginning of life or with human value. The American College of Obstetricians and Gynecologists states that “viability does not define the beginning of life or personhood,” but instead reflects the limits of contemporary medical intervention. ( 2 ) Human development proceeds continuously throughout pregnancy, regardless of whether survival outside the womb is medically possible at a given moment. ( 3 )
The Changing Threshold of Viability
Historically, viability was often placed near 28 weeks of gestation, reflecting the limitations of neonatal care in the mid-20th century. At that time, neonatal researchers observed that “survival prior to 28 weeks was rare,” largely due to immature lungs and the absence of effective respiratory support. ( 4 )
Advances in neonatal medicine—including antenatal corticosteroids, surfactant therapy, advanced ventilation, and highly specialized neonatal intensive care—have steadily shifted this threshold earlier. Contemporary studies now document survival at 22–23 weeks of gestation, particularly in specialized care settings. While survival rates at 22 weeks remain limited, researchers consistently report that “outcomes improve substantially with each additional week of gestation,” underscoring the developmental continuum of early human life. ( 5 ) ( 6 )
As neonatal medicine continues to progress, the shifting boundary of viability illustrates that this standard is shaped by medical capability rather than biology itself. The changing threshold invites careful reflection on how society understands, protects, and values human life at its most vulnerable stages.
Surfactant Therapy
Surfactant replacement therapy has been a transformative advance in the care of premature infants with neonatal respiratory distress syndrome (RDS). RDS is closely linked to lung immaturity and surfactant deficiency; clinical literature explains that neonatal RDS “occurs from a deficiency of surfactant” in underdeveloped lungs. ( 7 ) Premature infants often lack sufficient functional surfactant to stabilize the alveoli, leading to breathing failure and life-threatening complications shortly after birth. ( 8 )
Following the development of exogenous surfactant, randomized clinical trials consistently demonstrated substantial improvements in outcomes for preterm infants with RDS. Reviews of this therapy report that surfactant administration significantly reduced both neonatal mortality and pulmonary air leaks, marking a major shift in neonatal survival. Subsequent medical consensus has established surfactant therapy as a standard of care, with evidence showing it reduces mortality and the risk of air leak in vulnerable premature infants. Large systematic reviews further conclude that early surfactant treatment lowers the risk of acute lung injury and decreases neonatal death when compared with delayed intervention. ( 9 )
Together, these findings confirm that surfactant therapy dramatically improves survival and reduces serious complications in premature infants with RDS, underscoring the importance of providing life-sustaining care even in the most fragile and challenging circumstances.
Extracorporeal Membrane Oxygenation (ECMO)
Extracorporeal Membrane Oxygenation (ECMO) is an advanced life-support technology used in critically ill newborns when the heart or lungs cannot provide adequate oxygenation despite maximal treatment. ( 10 ) ECMO works by circulating blood through an external circuit, where oxygen is added and carbon dioxide is removed, allowing the infant’s heart and lungs time to rest and recover. ( 11 )
In neonatal care, ECMO is most commonly used for severe respiratory failure, including persistent pulmonary hypertension of the newborn, meconium aspiration syndrome, overwhelming infection, and selected congenital conditions. Because ECMO requires anticoagulation and carries a significant risk of bleeding, it is generally reserved for late-preterm and term infants rather than very premature newborns.
Although ECMO does not determine fetal viability on its own, it demonstrates how advances in neonatal medicine continue to extend the limits of survival after birth. ( 12 ) Each successful use of ECMO reflects the lifesaving potential of medical innovation for the most vulnerable infants.
Therapeutic Hypothermia (Cooling Therapy)
Therapeutic hypothermia (cooling therapy) is an evidence-based treatment for term and near-term newborns with moderate to severe hypoxic-ischemic encephalopathy (HIE), a form of brain injury caused by reduced oxygen and blood flow around the time of birth. Large randomized clinical trials have shown that lowering an infant’s body temperature shortly after birth slows metabolic injury in the brain and significantly improves outcomes. A landmark multicenter study reported that “whole-body hypothermia reduces the risk of death or disability” in infants with moderate or severe HIE. ( 13 )
Clinical guidance from the American Academy of Pediatrics affirms this conclusion, stating that “data from large randomized clinical trials indicate that therapeutic hypothermia…is an effective therapy for neonatal encephalopathy” when initiated within the appropriate therapeutic window. ( 14 ) Systematic reviews further demonstrate that cooling therapy improves survival and neurodevelopment, with the Cochrane Collaboration concluding that therapeutic hypothermia “reduces mortality and major neurodevelopmental disability at 18 to 24 months of age” in eligible newborns. ( 15 )
High-Frequency Oscillatory Ventilation (HFOV)
High-Frequency Oscillatory Ventilation (HFOV) is a form of mechanical ventilation used in newborns with severe respiratory failure, often as a rescue strategy when conventional ventilation fails to provide adequate gas exchange. HFOV delivers extremely rapid oscillations using very small tidal volumes—often less than anatomical dead space—while maintaining a relatively constant mean airway pressure to keep the lungs recruited and evenly inflated. ( 16 )
Because HFOV avoids large breath-to-breath volume changes, it is widely described as a lung-protective approach. Clinical reviews explain that HFOV uses low tidal volumes and constant distending pressure, reducing the repetitive opening and closing of alveoli associated with ventilator-induced lung injury. ( 17 ) While experimental studies demonstrate reduced lung injury with this strategy, large clinical trials show mixed results when HFOV is compared with conventional ventilation, indicating that it is not universally superior but remains valuable in specific clinical circumstances. ( 18 )
HFOV continues to play an important role in neonatal intensive care, reflecting ongoing medical innovation aimed at supporting the most fragile infants while carefully balancing life-sustaining respiratory support with protection of the developing lungs.
Real-World Survival Data
Viability—the ability of a preterm infant to survive outside the womb with medical support—has shifted in recent decades as neonatal care has advanced. Once commonly placed around 24 weeks’ gestation, survival is now documented at 22 and 23 weeks, particularly when active treatment is provided. ( 19 )
Recent U.S. multicenter data from the NICHD Neonatal Research Network (2013–2018) show that “survival among actively treated infants was 30.0% at 22 weeks and 55.8% at 23 weeks.” ( 19 ) When all live-born infants are included—regardless of treatment—survival is lower, reflecting the critical role that care decisions play: “Survival to discharge was 10.9% for live-born infants at 22 weeks.” ( 19 )
These gains are associated with established medical practices such as antenatal corticosteroids, surfactant therapy, advanced respiratory support, and specialized neonatal intensive care. Still, outcomes at these gestational ages remain uncertain, and long-term complications are common among survivors. ( 19 )
Survival also varies widely by location. Studies show that hospital policies strongly influence outcomes, with some centers actively treating most infants born at 22 weeks and others offering little or no intervention. One analysis found that rates of active treatment at 22 weeks ranged from 8% to 100% across U.S. hospitals. ( 20 ) Broader population studies confirm significant regional and institutional differences in care. ( 21 )
Page Citations & Notes
1. Royal College of Obstetricians and Gynaecologists. “Perinatal Management of Pregnant Women at the Threshold of Infant Viability (The Obstetric Perspective): Scientific Impact Paper No. 41.” RCOG, February 2014. Referenced for: viability as a clinical judgment shaped by gestational age, development, and available neonatal care rather than a single universal gestational age.
2. American College of Obstetricians and Gynecologists. “Facts Are Important: Understanding and Navigating Viability.” ACOG, n.d. Referenced for: viability as a medical concept tied to the capacity for survival outside the uterus with medical support, not a marker of personhood or the beginning of life.
3. American College of Obstetricians and Gynecologists. “ACOG Statement on ‘Personhood’ Measures.” ACOG, November 9, 2022. Referenced for: the distinction between viability as a medical threshold and claims about legal or moral personhood.
4. Stoll, Barbara J., et al. “Neonatal Outcomes of Extremely Preterm Infants From the NICHD Neonatal Research Network.” Pediatrics 126, no. 3 (2010): 443–56. Referenced for: historical survival limits in extremely preterm infants and the steep increase in survival with each additional week of gestation.
5. Rysavy, Matthew A., et al. “Between-Hospital Variation in Treatment and Outcomes in Extremely Preterm Infants.” New England Journal of Medicine 372, no. 19 (2015): 1801–11. Referenced for: survival at 22–23 weeks being strongly influenced by active treatment, with outcomes improving substantially with each additional week of gestation.
6. Bell, Edward F., et al. “Mortality, In-Hospital Morbidity, Care Practices, and 2-Year Outcomes for Extremely Preterm Infants in the US, 2013–2018.” JAMA 327, no. 3 (2022): 248–63. Referenced for: more recent survival data showing that the practical threshold of viability has shifted earlier with advances in neonatal care.
7. Avery, Mary Ellen, and Jere Mead. “Surface Properties in Relation to Atelectasis and Hyaline Membrane Disease.” AMA Journal of Diseases of Children 97, no. 5 (1959): 517–23. Referenced for: the classic finding that neonatal respiratory distress syndrome is linked to surfactant deficiency in immature lungs.
8. Jobe, Alan H., and Eduardo Bancalari. “Bronchopulmonary Dysplasia.” American Journal of Respiratory and Critical Care Medicine 163, no. 7 (2001): 1723–29. Referenced for: the role of exogenous surfactant in reducing the severity of respiratory distress syndrome and decreasing the need for more injurious ventilation.
9. Sweet, David G., et al. “European Consensus Guidelines on the Management of Respiratory Distress Syndrome: 2022 Update.” Neonatology 120, no. 1 (2023): 3–23. Referenced for: surfactant therapy as established standard care in modern neonatal respiratory management.
10. Wild, K. Taylor, et al. “Extracorporeal Life Support Organization (ELSO): Guidelines for Neonatal Respiratory Failure.” ELSO, updated 2020. Referenced for: ECMO as advanced life support for newborns with severe respiratory failure when conventional treatment is not enough.
11. Fletcher, Katherine, et al. “An Overview of Medical ECMO for Neonates.” Seminars in Perinatology 42, no. 2 (2018): 115–21. Referenced for: how ECMO oxygenates blood and removes carbon dioxide externally, and why it is generally used in selected neonatal cases rather than the most premature infants.
12. Tonna, Joseph E., et al. “Extracorporeal Life Support Organization Registry International Report 2024.” ASAIO Journal 70, no. 3 (2024). Referenced for: contemporary outcome data showing the continuing survival benefit of neonatal respiratory ECMO in appropriate cases.
13. Shankaran, Seetha, et al. “Whole-Body Hypothermia for Neonates With Hypoxic-Ischemic Encephalopathy.” New England Journal of Medicine 353, no. 15 (2005): 1574–84. Referenced for: the landmark finding that whole-body hypothermia reduces the risk of death or disability in newborns with moderate or severe HIE.
14. Papile, Lu-Ann, et al. “Hypothermia and Neonatal Encephalopathy.” Pediatrics 133, no. 6 (2014): 1146–50. Referenced for: American Academy of Pediatrics guidance affirming therapeutic hypothermia as an effective treatment when used within the proper therapeutic window.
15. Jacobs, Samantha E., et al. “Cooling for Newborns With Hypoxic Ischaemic Encephalopathy.” Cochrane Database of Systematic Reviews 2013, no. 1 (2013): CD003311. Referenced for: evidence that cooling therapy reduces mortality and major neurodevelopmental disability at follow-up.
16. Froese, Alison B., and John P. Kinsella. “High-Frequency Oscillatory Ventilation: Lessons From the Neonatal/Pediatric Experience.” Critical Care Medicine 33, suppl. 3 (2005): S115–21. Referenced for: HFOV using very small tidal volumes with a relatively constant mean airway pressure to support gas exchange while protecting the lungs.
17. Himmelstein, Robert D., and colleagues. “High-Frequency Oscillator in the Neonate.” In StatPearls. Treasure Island, FL: StatPearls Publishing, 2024. Referenced for: HFOV as a lung-protective ventilation strategy used in neonates, especially when conventional ventilation is failing.
18. Cools, Fien, et al. “Elective High Frequency Oscillatory Ventilation Versus Conventional Ventilation for Acute Pulmonary Dysfunction in Preterm Infants.” Cochrane Database of Systematic Reviews 2015, no. 3 (2015): CD000104. Referenced for: the mixed trial evidence showing that HFOV can reduce some forms of lung injury but is not uniformly superior to conventional ventilation in all outcomes.
19. Bell, Edward F., et al. “Mortality, In-Hospital Morbidity, Care Practices, and 2-Year Outcomes for Extremely Preterm Infants in the US, 2013–2018.” JAMA 327, no. 3 (2022): 248–63. Referenced for: the reported survival figures on the page, including 30.0% survival among actively treated infants at 22 weeks and 55.8% at 23 weeks, as well as lower survival when all live-born infants are included.
20. Mehler, Kathryn, et al. “Survival Among Infants Born at 22 or 23 Weeks’ Gestation Following Active Prenatal and Postnatal Care.” JAMA Pediatrics 170, no. 7 (2016): 671–77. Referenced for: wide hospital-to-hospital variation in active treatment at 22 weeks, including the page’s point that rates ranged from 8% to 100% across hospitals.
21. Venkatesh, Kartik K., et al. “Trends in Active Treatment of Live-Born Neonates Between 22 Weeks 0 Days and 25 Weeks 6 Days of Gestation in the US, 2014–2019.” JAMA Network Open 5, no. 8 (2022): e2225877. Referenced for: regional variation in postnatal life support at 22 and 23 weeks and the importance of institutional treatment patterns in survival outcomes.
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