A term used to denote the power a newborn child possesses of continuing its independent existence. That stage of fetal development when the life of the unborn child may be continued indefinitely outside the womb by natural or artificial life-support systems. The constitutionality of this statutory definition (V.A.M.S. (Mo.),188.015) was upheld in Planned Parenthood of Central Mo. v. Danforth, 428 U.S. 52,96 S.Ct 2831, 49 L.Ed.2d 788. For purposes of abortion regulation, viability is reached when, in the judgement of the attending physician on the particular facts of the case before her, there is a reasonable likelihood of the fetuses' sustained survival outside the womb, with or without artificial support. Colautti v. Franklin, 439 U.S. 379,388, 99 S.Ct. 675, 682, 58 L.Ed.2d 596. See Also Viable; Viable Child. Medical viability Fetal viability is generally considered to begin at 23 or 24 weeks gestational age in the United States. There is no sharp limit of development, gestational age, or weight at which a human fetus automatically becomes viable. According to one study, between 2013 and 2018 at United States academic medical centers, the percentage of newborns who survived long enough to leave the hospital was 30% at 22 weeks, 55% at 23 weeks, 70% at 24 weeks, and 80% of those born at 25 weeks gestational age. Between 2010 and 2014, babies in the United States had an approximately 70% survival rate when born under weight of 500 g (1.10lb), an increase from a 30.8% survival rate between 2006 and 2010. A baby's chances for survival increases 3 to 4 percentage points per day between 23 and 24 weeks of gestation, and about 2 to 3 percentage points per day between 24 and 26 weeks of gestation. After 26 weeks the rate of survival increases at a much slower rate because survival is high already. Prognosis depends also on medical protocols on whether to resuscitate and aggressively treat a very premature newborn, or whether to provide only palliative care, in view of the high risk of severe disability of very preterm babies. According to a Stanford University study on babies born in the most advanced US hospitals between 2013 and 2018, at 23 weeks, 55% of infants survive a preterm birth long enough to be discharged from the hospital, usually months later. Most of these infants experienced some form of significant neurodevelopmental impairment, such as cerebral palsy. Most were re-hospitalized for