When Babies Are Born at 22 or 23 Weeks: What a New Global Study Reveals About Survival Around the World

A plain-language guide to the largest international comparison yet of outcomes for extremely premature infants

A new international study followed over 5,000 babies born at 22 or 23 weeks of pregnancy — roughly four months early — across 11 countries, and found that survival to going home depended heavily on where a baby was born: in the strongest-performing countries, well over half of 22-week babies survived, versus closer to 1 in 10 elsewhere. This guide explains that gap, why it exists, and what it means for families.

Why Babies Born This Early Are So Hard to Predict For

A full-term pregnancy lasts about 40 weeks, so a baby born at 22 or 23 weeks arrives roughly four months before their due date, at a point when their lungs, skin, brain, and other organs are still very early in development. Doctors call this the edge of "viability" — the earliest point at which a baby has any realistic chance of surviving outside the womb, even with the most intensive medical support available. Because so few babies are born this early, and because the ones who are born this early differ so much from one another in size, condition at birth, and the complications they face, predicting any individual baby's outcome is genuinely difficult, even for experienced doctors. What has been less well understood, until recently, is how much of that unpredictability comes from the baby, and how much comes from differences in medical practice and hospital policy from one country to the next — which is precisely the question this new study set out to answer.

How Uncertain and How Variable This Care Used to Be

The study at the center of this article, published in 2025 by an international research collaboration called the International Network for Evaluation of Outcomes (iNeo) of Neonates ^[1], set out to measure exactly this kind of persistent, country-to-country variation — and to understand why it matters, it helps to look back at how recent and how uneven progress at this gestational age has been. As recently as the 1990s and early 2000s, babies born at 22 or 23 weeks were, in most parts of the world, not offered active resuscitation at all — the near-universal assumption was that survival was essentially impossible, and the focus was on comfort rather than treatment. That assumption began to shift country by country, unevenly and often slowly, as individual hospitals and then national programs started offering intensive care more proactively to a subset of these babies and tracking what happened. A large multi-country analysis published in 2019 pooled results from that period and estimated that, among babies who did receive active treatment, roughly 1 in 4 born at 22 weeks and a little under 2 in 5 born at 23 weeks survived — numbers that shocked some clinicians at the time and reassured others, and that have been widely quoted ever since ^[2]. Even earlier, in 2017, the same international research collaboration behind the newest study had already shown, by comparing ten countries' newborn intensive care registries, that survival for very premature babies more broadly varied a great deal depending on which country a baby was born in ^[3]. Since then, individual countries have told their own versions of this story: Japan's national data showed unusually high survival at 22–23 weeks linked to specific, consistently applied national practices ^[4]; Sweden tracked survival across three time periods from the mid-2000s to 2019 and found it rising as national guidance became more supportive of active treatment ^[5]; and in England and Wales, a 2019 change in national guidance — moving away from a strict cutoff and toward individualized decisions for each family — was followed by a real, measurable increase in survival at 22 weeks ^[6]. What none of this earlier work could do was bring a large, recent, single, carefully standardized comparison across many countries together at once — which is exactly the gap this 2025 study was designed to fill.

What Researchers Did: A Global Registry, Not a Clinical Trial

To answer this question, iNeo — a registry consortium that pools carefully collected, anonymized birth records from newborn intensive care units around the world, rather than running an experiment — brought together data from 11 national or regional newborn-care registries covering 12 countries or regions: Australia and New Zealand, Brazil, Canada, Finland, Israel, Japan, Spain, Sweden, Switzerland, the Tuscany region of Italy, and the United Kingdom ^[1]. This was an observational cohort of 5,019 infants born between 2015 and 2021, all of whom had received active intensive care after birth — meaning breathing support or other treatment aimed at helping them survive, rather than comfort care alone. Of these, 846 babies were born at 22 weeks and 4,173 at 23 weeks. Importantly, the study only includes babies who were actively treated; it does not include babies who were stillborn or who died in the delivery room without treatment, so it cannot tell us what would happen to every pregnancy at this stage — only what happens for babies whose families and doctors chose, together, to pursue intensive care. Researchers also carefully adjusted their comparisons to account for differences between babies, such as birth weight, sex, and whether a baby was a twin or triplet, so that the country-to-country comparisons would be as fair as possible.

What the Study Found: A Wide and Consistent Gap Between Countries

The results showed real, statistically meaningful differences in outcomes depending on where a baby was born. After accounting for differences between individual babies, the chance of surviving to go home ranged from about 9% to 64% for babies born at 22 weeks, and from about 16% to 80% for babies born at 23 weeks, depending on the country or region — so in the best-performing networks, well over half of babies born at 22 weeks went home, while in the lowest-performing network in this dataset it was closer to 1 in 10. Two countries illustrate how far outcomes diverged from what would be statistically expected given each network's own mix of babies: Japan's network had survival at 22 weeks roughly double what its babies' health profiles would predict, while Brazil's network had survival far below what would be predicted for its babies. The gap was somewhat narrower, but still substantial, at 23 weeks. The study also looked at serious complications, including bleeding in the brain (called periventricular hemorrhage, or bleeding into or around the fluid-filled spaces of the brain) and a serious eye condition called retinopathy of prematurity (abnormal blood-vessel growth in the eye that can threaten vision if untreated), and found that these, too, varied significantly by country — sometimes in ways that did not perfectly track with survival, meaning a country with high survival did not always also have the lowest complication rates. One encouraging, very practical finding: for babies born at either 22 or 23 weeks, each extra day spent in the womb — even within the same "week" — meaningfully improved the odds of survival, underscoring that every day of a pregnancy at this stage matters.

What This Means for Families Making These Decisions

If your family is facing a possible birth at 22 or 23 weeks, the single most important message from this study is that outcomes at this gestational age are not fixed or universal — they depend heavily on the specific hospital, team, and country providing care, and on your baby's individual circumstances, not on a single number you might read online. National and international summary statistics, including the ones in this study, describe groups of babies, not your baby, and your care team is best positioned to talk through what your particular hospital's own outcomes and practices look like, and what treatment options and support are realistically available to you. The study's authors were explicit that they do not see it as a goal for every country to have identical survival numbers — some of the difference may reflect real, thoughtfully considered differences in how societies and medical communities approach care at this uncertain stage, not simply better or worse care, a nuance echoed in other work examining how different countries set their own thresholds for offering intensive care ^[7]. What matters most for your own decision-making is an honest, detailed conversation with your neonatal team about what to expect at your specific hospital, including its own experience with babies at this exact gestational age. For families who want to understand how outcomes can also vary between hospitals within a single country, not just between countries, In[Neo]Sight's related coverage of hospital-level differences in South Korea (https://inneosight.org/en-US/articles/periviable22-23wk-knn2026) offers a complementary look at this same question on a smaller geographic scale, and our broader piece on global survival-gap inequities (https://inneosight.org/en-US/articles/global-eptsurvival-inequities2025) places these findings in worldwide context.

What Researchers Are Working On Next

The study's authors were careful to frame their findings as a starting point rather than a final answer. Because the study only followed babies to the point of hospital discharge, it could not tell us anything about how these children develop later in childhood — a gap that future research urgently needs to fill, since long-term development, not just short-term survival, is often what matters most to families. Researchers also want to understand, in much more specific and actionable detail, exactly which practices — timing of medications given to mothers before birth, delivery methods, specific approaches to breathing support — explain why some countries' babies do so much better, so that promising, safe practices can potentially be shared and adapted elsewhere, building on earlier work calling for exactly this kind of practice-sharing research ^[8]. Other researchers continue to study how doctors, hospitals, and whole health systems can improve the consistency and quality of counseling that families receive at this stage, so that every family — regardless of country — has access to clear, honest, individualized information to help guide their decisions together with their care team ^[9]. The international collaboration behind this study, which has been building and refining this kind of cross-country comparison for close to a decade, has already signaled that continued tracking and expansion of this registry work is a priority ^[10].

References

1. Isayama T, Norman M, Kusuda S, et al; International Network for Evaluation of Outcomes (iNeo) of Neonates. Outcomes of Preterm Infants Born at 22 to 23 Weeks' Gestation in 11 International Neonatal Networks. JAMA Pediatrics. 2025;179(11):1183-1193. doi:10.1001/jamapediatrics.2025.2958 ↩
2. Myrhaug HT, Brurberg KG, Hov L, Markestad T. Survival and Impairment of Extremely Premature Infants: A Meta-analysis. Pediatrics. 2019;143(2):e20180933. doi:10.1542/peds.2018-0933 ↩
3. Helenius K, Sjörs G, Shah PS, et al; International Network for Evaluating Outcomes (iNeo) of Neonates. Survival in Very Preterm Infants: An International Comparison of 10 National Neonatal Networks. Pediatrics. 2017;140(6):e20171264. doi:10.1542/peds.2017-1264 ↩
4. Isayama T, Miyakoshi K, Namba F, et al. Survival and Unique Clinical Practices of Extremely Preterm Infants Born at 22-23 Weeks' Gestation in Japan: A National Survey. Arch Dis Child Fetal Neonatal Ed. 2024;110(1):17-22. doi:10.1136/archdischild-2023-326355 ↩
5. Farooqi A, Hakansson S, Serenius F, et al. One-Year Survival and Outcomes of Infants Born at 22 and 23 Weeks of Gestation in Sweden 2004-2007, 2014-2016 and 2017-2019. Arch Dis Child Fetal Neonatal Ed. 2023;109(1):10-17. doi:10.1136/archdischild-2022-325164 ↩
6. Smith LK, van Blankenstein E, Fox G, et al; MBRRACE-UK Perinatal Surveillance Group. Effect of National Guidance on Survival for Babies Born at 22 Weeks' Gestation in England and Wales: Population Based Cohort Study. BMJ Med. 2023;2(1):e000579. doi:10.1136/bmjmed-2023-000579 ↩
7. Wilkinson D, Verhagen E, Johansson S. Thresholds for Resuscitation of Extremely Preterm Infants in the UK, Sweden, and Netherlands. Pediatrics. 2018;142(suppl 1):S574-S584. doi:10.1542/peds.2018-0478I ↩
8. Guillén Ú, Zupancic JAF, Litt JS, et al. Community Considerations for Aggressive Intensive Care Therapy for Infants <24+0 Weeks of Gestation. J Pediatr. 2024;268:113948. doi:10.1016/j.jpeds.2024.113948 ↩
9. Rysavy MA, Mehler K, Oberthür A, et al. An Immature Science: Intensive Care for Infants Born at ≤23 Weeks of Gestation. J Pediatr. 2021;233:16-25.e1. doi:10.1016/j.jpeds.2021.03.006 ↩
10. Shah PS, Lui K, Reichman B, et al. The International Network for Evaluating Outcomes (iNeo) of Neonates: Evolution, Progress and Opportunities. Transl Pediatr. 2019;8(3):170-181. doi:10.21037/tp.2019.07.06 ↩