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Fetal viability is the ability of a human fetus to survive outside the uterus. Viability depends upon factors such as birth weight, gestational age, and the availability of advanced medical care. In low-income countries, more than 90% of extremely preterm newborns (less than 28 weeks gestational age) die due to a lack of said medical care; in high-income countries, the vast majority of these newborns survive.
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As of 2022, the world record for the lowest gestational age newborn to survive is held by Curtis Zy-Keith Means, who was born on 5 July 2020 in the United States, at 21 weeks and 1 day gestational age, weighing 420 grams.
According to the McGraw-Hill medical dictionary, a nonviable fetus is "an expelled or delivered fetus which, although living, cannot possibly survive to the point of sustaining life independently, even with support of the best available medical therapy". A legal definition states: "Nonviable means not capable of living, growing, or developing and functioning successfully. It is the antithesis of viable, which is defined as having attained such form and development of organs as to be normally capable of living outside the uterus." Wolfe
Various jurisdictions have different legal definitions of viability. In Ireland, under the Health (Regulation of Termination of Pregnancy) Act 2018, fetal viability is defined as "the point in a pregnancy at which, in the reasonable opinion of a medical practitioner, the foetus is capable of survival outside the uterus without extraordinary life-sustaining measures" Definitions.
For purposes of abortion regulation, viability is reached when, in the judgement of the attending physician on the particular facts of the case before him or 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.
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.
, showing viability and point of 50% chance of survival ( limit of viability) at bottom. Weeks and months numbered by gestation,]]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 respiratory illnesses or other medical problems during the first two years of life. Some used adaptive equipment such as walkers or feeding tubes, but most could feed themselves when they were 2 years old. Most had typical vision and hearing.
Indian Law considers the period of viability to be the period after 28 weeks of gestational age.
As of the mid-2000s, the limit of viability is considered to be around 24 weeks, although the incidence of major disabilities remains high at this point. Neonatologists generally would not provide intensive care at 23 weeks, but would from 26 weeks. Roe v. Wade, 410 U.S. 113 (1973) ("viability is usually placed at about seven months (28 weeks) but may occur earlier, even at 24 weeks.") Retrieved 4 March 2007.
Different jurisdictions have different policies regarding the resuscitation of extremely premature newborns, that may be based on various factors such as gestational age, weight and medical presentation of the baby, the desires of parents and medical practitioners. The high risk of severe disability of very premature babies or of mortality despite medical efforts lead to ethical debates over quality of life and futile medical care, but also about the sanctity of life as viewed in various religious doctrines.
As of 2022, the world record for the lowest gestational age newborn to survive is held by Curtis Zy-Keith Means, who was born on 5 July 2020 in the United States, at 21 weeks and 1 day gestational age, weighing 420 grams.
A preterm birth, also known as premature birth, is defined as babies born alive before 37 weeks of pregnancy are completed. There are three types of preterm births: extremely preterm (less than 28 weeks), very preterm (28 to 32 weeks) and moderate to late preterm (32 to 37 weeks).
Several types of health problems also influence fetal viability. For example, breathing problems, congenital abnormalities or malformations, and the presence of other severe diseases, especially infection, threaten the survival of the neonate.
Other factors may influence survival by altering the rate of organ maturation or by changing the supply of oxygen to the developing fetus.
The mother's health plays a significant role in the child's viability. Diabetes in the mother, if not well controlled, slows organ maturation; infants of such mothers have a higher mortality. Severe high blood pressure before the 8th month of pregnancy may cause changes in the placenta, decreasing the delivery of nutrients and/or oxygen to the developing fetus and leading to problems before and after delivery.
Rupture of the fetal membranes before 24 weeks of gestation with loss of amniotic fluid markedly decreases the baby's chances of survival, even if the baby is delivered much later.
The quality of the facility—whether the hospital offers neonatal critical care services, whether it is a Level I pediatric trauma care facility, the availability of corticosteroids and other medications at the facility, the experience and number of physicians and nurses in neonatology and obstetrics and of the providers has a limited but still significant impact on fetal viability. Facilities that have obstetrical services and emergency rooms and operating facilities, even if smaller, can be used in areas where higher services are not available to stabilize the mother and fetus or neonate until they can be transferred to an appropriate facility.
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