The objective of this paper is to review observational studies that addressed the survival of pre-viable gestations in the United States. We searched PubMed, Ovid, CINAHL, and Web of Knowledge for studies reporting survival of infants born at <24 gestational weeks and/or <500g in the United States and published between January 2003 and January 2013. The full texts of 70 articles were examined and a total of 15 studies qualified and were selected. We analyzed fixed-effect and random-effects models for eight studies on survival to discharge. Pooled survival to discharge in the random-effects model was 45.9% (95% CI: 41.1-51.7) and 39.7% in the fixed-effect model (95% CI: 38.8-40.7). Studies differed by pre-viable survival measures and epochs (1985-2009). Protective factors included antenatal corticosteroids, neonatal resuscitation, and intensive care. The current survival threshold for pre-viable infants warrants reconsideration of the limits of viability. Protective factors that enhance survival should be considered in the management of these infants.
Keywords: Extremely low birth weight; Extremely preterm birth; Periviable; Pre-viable; Pregnancy; Survival.
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