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Estimates of gestational age–specific survival vary significantly across hospitals, regions, and countries and are influenced by a number of factors that can make unbiased comparisons challenging.
- •
Survival among live periviable births at 22 to 25 weeks of gestation has incrementally improved since the 1950s, with continued gains over the past decade.
- •
Provision of active treatment, particularly at 22 and 23 weeks of gestation, varies widely among centers and countries, and this variation has a
Survival of Infants Born at Periviable Gestational Ages
Section snippets
Key points
Historical perspectives
The survival of extremely low birth weight (ELBW; birth weight ≤1000 g) infants, including periviable infants, has improved consistently over the past 7 decades. In the 1940s, death was the expected outcome for all ELBW infants born in developed nations around the world.3 Beginning in the 1950s and 1960s, the probability of survival for ELBW infants among several centers in the United States and the United Kingdom increased to 10% to 30% as understanding of neonatal physiology improved and the
Estimates of gestational age–specific survival
During the past 5 years, large cohort studies from developed nations in North America,11, 12, 13, 20, 21 South America,22 Europe,14, 15, 23, 24, 25 Asia,18, 19, 26 and Australia27 have reported estimates of gestational age–specific survival following periviable birth. Direct comparisons of estimated survival rates among these studies are limited, however, by potential biases introduced from differences in the data sources, ascertainment of death, selection of denominators, and definitions of
Recommendations and guidelines for perinatal care
Some of the variation in survival observed in Fig. 2 may be attributable to variation in the approach to perinatal care based on guideline statements from professional organizations and scientific societies. In a systematic review of 31 national or international guidelines for perinatal care of periviable births in highly developed countries, there was substantial variation in recommendations. Sixty-eight percent of guideline statements supported comfort care at 22 weeks of gestation and 65%
Cohort Selection
Differences in the conduct of cohort studies are important to understand when interpreting and comparing gestational age–specific survival rates. This is particularly relevant when studies use different numerators (eg, death in the delivery room, death before 28 days, death before hospital discharge, death before 1 year) and denominators (eg, fetus alive at maternal admission and >20 weeks of gestation, all live births, inborn live births, live births receiving active treatment, infants
Summary
In conclusion, survival among periviable births has improved since the 1950s, including over the past decade. There is wide variation in survival of periviable live births across developed countries and across different NICUs in the same country, although estimates of gestational age–specific survival are influenced by a number of factors that limit unbiased comparisons. Provision of active treatment, particularly at 22 and 23 weeks of gestation, varies widely among hospitals and developed
Acknowledgments
The review was supported, in part, by the National Institutes of Health under award K23 HL128942 (R.M. Patel). The authors would like to acknowledge the NICHD Neonatal Research Network, including Rosemary Higgins, MD, Abhik Das, PhD, and the GDB subcommittee, for graciously providing recent data on periviable survival.
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Conflicts of Interest: The authors have no conflicts of interest to report.