Survival and Impairment of Extremely Premature Infants: A Meta-analysis

CONTEXT: Survival of infants born at the limit of viability varies between high-income countries. OBJECTIVE: To summarize the prognosis of survival and risk of impairment for infants born at 22 + 0/7 weeks' to 27 + 6/7 weeks' gestational age (GA) in high-income countries. DATA SOURCES: We searched 9 databases for cohort studies published between 2000 and 2017 in which researchers reported on survival or neurodevelopmental outcomes. STUDY SELECTION: GA was based on ultrasound results, the last menstrual period, or a combination of both, and neurodevelopmental outcomes were measured by using the Bayley Scales of Infant Development II or III at 18 to 36 months of age. DATA EXTRACTION: Two reviewers independently extracted data and assessed the risk of bias and quality of evidence. RESULTS: Sixty-five studies were included. Mean survival rates increased from near 0% of all births, 7.3% of live births, and 24.1% of infants admitted to intensive care at 22 weeks' GA to 82.1%, 90.1%, and 90.2% at 27 weeks' GA, respectively. For the survivors, the rates of severe impairment decreased from 36.3% to 19.1% for 22 to 24 weeks' GA and from 14.0% to 4.2% for 25 to 27 weeks' GA. The mean chance of survival without impairment for infants born alive increased from 1.2% to 9.3% for 22 to 24 weeks' GA and from 40.6% to 64.2% for 25 to 27 weeks' GA. LIMITATIONS: The confidence in these estimates ranged from high to very low. CONCLUSIONS: Survival without impairment was substantially lower for children born at <25 weeks' GA than for those born later.