What makes these numbers remarkable is not only their magnitude but their consistency. Survival statistics for infants at the very edge of viability vary enormously between countries, and even between hospitals within the same country, because they depend on a tangled web of decisions: whether obstetricians transfer mothers before delivery, whether resuscitation is attempted at all, and how intensively each fragile organ system is managed afterward. The Japanese review addresses this complexity directly, linking outcomes not just to clinical technique but to the architecture of the healthcare system itself. Three structural pillars emerge from the analysis: regionalized perinatal care that promotes antenatal maternal transfer, a nationwide clinical network that benchmarks every participating center, and universal health insurance that removes financial barriers to intensive care.

The first pillar, regionalization, is deceptively simple. Rather than allowing extremely preterm labor to be managed wherever it happens to occur, Japan’s perinatal system encourages the transfer of the pregnant woman, not the newborn, to a facility equipped with the highest level of neonatal intensive care. This means the infant is born in the very place where ventilators, surfactant, specialized nursing and round-the-clock physician coverage already exist. Epidemiologic studies cited in the review show that outborn infants, those born outside tertiary centers and transported after delivery, fare substantially worse than inborn infants, a finding that transforms maternal transfer from a logistical preference into a life-saving intervention. The review also notes distinctive Japanese delivery practices, including cesarean delivery en caul, in which the infant is delivered still encased within the intact amniotic sac, a technique designed to protect the fragile head and umbilical cord during extraction and to allow a gentler transition to extrauterine life.

The second pillar is data. Since the establishment of the Neonatal Research Network of Japan, virtually every very low birth weight infant admitted to a participating neonatal intensive care unit has been entered into a central database, creating a continuous national audit of survival and morbidity. This infrastructure allows centers to compare their outcomes against national benchmarks, identify drift, and refine protocols in response to evidence rather than anecdote. The review emphasizes that this data-driven quality improvement cycle, in which outcomes are monitored continuously and fed back into clinical practice, is not an optional extra but a core mechanism sustaining Japan’s results. International comparisons conducted through networks such as the International Network for Evaluating Outcomes of very low birth weight, very preterm neonates have repeatedly shown that Japan’s survival figures at 22 and 23 weeks exceed those of the United States, Sweden and other high-income countries, while rates of severe intraventricular hemorrhage and necrotizing enterocolitis remain comparatively low.

The third pillar, universal health insurance, is often overlooked in discussions of neonatal outcomes, yet it underpins everything else. In Japan, the cost of prolonged intensive care, which can stretch across months and consume enormous resources, is not borne by individual families in ways that might pressure clinicians toward less aggressive management. The review suggests that this financial context supports a culture in which active resuscitation at 22 and 23 weeks is the default rather than the exception, and in which treatment decisions are framed primarily around physiology and prognosis rather than around cost.

Clinical practice itself, the review argues, is characterized by meticulous, individualized, pathophysiology-based management. This begins at the moment of birth with active resuscitation, including invasive respiratory support. Unlike centers in some countries that favor early non-invasive strategies such as continuous positive airway pressure, Japanese practice at these gestational ages frequently proceeds directly to intubation and mechanical ventilation, on the reasoning that the lungs of a 22-week infant, with surfactant deficiency and structural immaturity, cannot generate the transpulmonary pressures needed for gas exchange without direct support. The review situates this within international evidence, noting that while non-invasive ventilation strategies have been associated with reduced bronchopulmonary dysplasia in broader preterm populations, their application at the very limits of viability remains contested, and that Japanese centers have chosen invasive support as a deliberate strategy tailored to this extreme population.

Perhaps the most distinctive element of Japanese neonatal practice described in the review is echocardiography-guided hemodynamic management. Rather than treating blood pressure numbers in isolation, Japanese clinicians use functional echocardiography to assess cardiac output, ductal shunting, and ventricular performance, allowing targeted intervention for conditions such as patent ductus arteriosus and late-onset circulatory collapse. The review describes how routine echocardiography enables proactive diagnosis and tailor-made treatment of the ductus arteriosus, a vessel that in preterm infants often fails to close after birth and can steal blood from the systemic circulation, compromising perfusion of the brain, gut and kidneys. Japanese practice has historically favored active treatment of hemodynamically significant ductal shunting, in contrast to the expectant management approach that has gained ground in some Western centers. The review acknowledges that the effectiveness of these practices remains uncertain and that ongoing randomized trials, including recent studies comparing early treatment with expectant management of the ductus, will be essential to clarify which approach truly benefits infants at these gestational ages.

Neuroprotection receives equally intensive attention. The germinal matrix, the highly vascular region lining the ventricles of the premature brain, is exquisitely vulnerable to fluctuations in cerebral blood flow and pressure, and severe intraventricular hemorrhage remains one of the most devastating complications of extreme prematurity. Japanese management emphasizes stabilization of hemodynamics from the first minutes of life, careful control of carbon dioxide levels during ventilation, avoidance of excessive fluid administration, and meticulous handling to minimize stress responses. The review also describes the use of inhaled nitric oxide for persistent pulmonary hypertension of the newborn, standardized across Japanese centers even at extremely early gestational ages, and the recognition of late-onset circulatory collapse, a syndrome of adrenal insufficiency and hypotension appearing days to weeks after birth, as a distinct entity requiring targeted steroid therapy. Sedation and analgesia practices are also being reconsidered, with national surveys examining how best to balance stress relief against the hypotensive effects of opioids in ventilated infants.

Specialized nursing care forms the final layer of this package. The review highlights the role of Japanese neonatal nursing, with its historic emphasis on individualized developmental care, precise positioning using low-volatile organic compound polyurethane foam devices, and continuous observation of subtle clinical changes. Nurses in Japanese neonatal intensive care units are trained to detect early signs of deterioration, manage the delicate balance between handling necessary for treatment and the stress that handling imposes, and support families through what is often a months-long journey. This nursing infrastructure, the review suggests, is inseparable from the medical interventions, because the survival of an infant weighing 400 grams depends as much on the precision of daily care as on the sophistication of ventilator settings.

The review is careful to temper enthusiasm with caution. It notes that while survival has improved, neurodevelopmental outcomes at 2 to 3 years of corrected age remain a critical measure, and that the effectiveness of many individual practices, from echocardiography-guided circulatory management to specific neuroprotective strategies, has not been established through rigorous trials. The authors argue that what matters may not be any single intervention but the integration of multiple practices into a coherent package of care, delivered within a system that monitors outcomes continuously and refines strategies in response to evidence. For clinicians and policymakers worldwide grappling with how to approach infants born at the very edge of viability, the Japanese experience offers a compelling, if not yet fully proven, template: regionalize care, benchmark relentlessly, remove financial barriers, and treat each infant not as a statistical category but as a physiological individual whose fragile organ systems demand pathophysiology-based, individualized management from the first breath onward.

Subject of Research: Neonatal outcomes and care practices for infants born at 22-23 weeks' gestation in Japan

Article Title: Japan at the limits of viability: national experience and evolving outcomes of infants born at 22–23 weeks’ gestation

Article References: Isayama, T., Nakanishi, H., Konishi, M., Kokubo, M., Fujimura, M., Hirano, S., & Kusuda, S. (2026). Japan at the limits of viability: national experience and evolving outcomes of infants born at 22–23 weeks’ gestation. Pediatric Research. https://doi.org/10.1038/s41390-026-05266-z

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05266-z

Keywords: extreme prematurity, limits of viability, neonatal intensive care, Japan, 22 weeks gestation, 23 weeks gestation, survival rates, intraventricular hemorrhage, patent ductus arteriosus, echocardiography, neuroprotection, Neonatal Research Network of Japan