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Fetal viability is the ability of a human fetus to survive outside the uterus. Medical viability is generally considered to be between 23 and 24 weeks gestational age. Viability depends upon factors such as
birth weight Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is , with the normative range between . On average, babies of South Asian and Chinese descent weigh about . As far as low birth weigh ...
, gestational age, and the availability of advanced medical care. In
low-income countries A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
, half of newborns born at or below 32 weeks gestational age died due to a lack of medical access; in
high-income countries A high-income economy is defined by the World Bank as a nation with a gross national income per capita of US$12,696 or more in 2020, calculated using the Atlas method. While the term "high-income" is often used interchangeably with "First World" a ...
, the vast majority of newborns born above 24 weeks gestational age survive. As of 2022, the
world record A world record is usually the best global and most important performance that is ever recorded and officially verified in a specific skill, sport, or other kind of activity. The book ''Guinness World Records'' and other world records organization ...
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.


Definitions

''Viability'', as the word has been used in the United States constitutional law since '' Roe v. Wade'', is the potential of the fetus to survive outside the uterus after birth, natural or induced, when supported by up-to-date medicine. Fetal viability depends largely on the fetal organ maturity, and environmental conditions. According to Websters Encyclopedic Unabridged Dictionary of the English Language, viability of a fetus means having reached such a stage of development as to be capable of living, under normal conditions, outside the uterus. Viability exists as a function of biomedical and technological capacities, which are different in different parts of the world. As a consequence, there is, at the present time, no worldwide, uniform gestational age that defines viability. 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." olfe v. Isbell, 291 Ala. 327, 329 (Ala. 1973) Various jurisdictions have different legal definitions of viability. In Ireland, under the
Health (Regulation of Termination of Pregnancy) Act 2018 The Health (Regulation of Termination of Pregnancy) Act 2018 ( Act No. 31 of 2018; previously Bill No. 105 of 2018) is an Act of the Oireachtas (Irish parliament) which defines the circumstances and processes within which abortion may be legally ...
, 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." efinitions (Part 2)(8)


Black's law dictionary 6th edition

Viability. Capable of living. 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 Palliative care (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...
, 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 Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between ...
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 Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, stiff muscles, weak muscles, and tremors. There may be problems with sensat ...
. 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.


Period of viability

Beliefs about viability vary by country. Medical decisions regarding the resuscitation of extremely preterm infants (EPI) deemed to be in the "grey zone" usually take into account weight and gestational age, as well as parental views. One 2018 study showed that there was a significant difference between countries in what was considered to be the "grey zone": the "grey zone" was considered to be 22 to 23 weeks in Sweden, 23 to 24 weeks in the UK, and 24 to 26 weeks in the Netherlands. Whether the fetus is in the period of viability may have legal ramifications as far as the fetus' rights of protection are concerned. Traditionally, the period of viability referred to the period after the twenty-eighth week.


United States Supreme Court

The United States Supreme Court stated in '' Roe v. Wade'' (1973) that viability, defined as the "interim point at which the fetus becomes ... potentially able to live outside the mother's womb, albeit with artificial aid", Roe v. Wade, 410 U.S. 113, 160, 93 S.Ct. 705, 730 (1973). "is usually placed at about seven months (28 weeks) but may occur earlier, even at 24 weeks." The 28-week definition became part of the "trimester framework" marking the point at which the "compelling state interest" (under the doctrine of
strict scrutiny In U.S. constitutional law, when a law infringes upon a fundamental constitutional right, the court may apply the strict scrutiny standard. Strict scrutiny holds the challenged law as presumptively invalid unless the government can demonstrate th ...
) in preserving potential life became possibly controlling, permitting states to freely regulate and even ban
abortion Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion"; these occur in approximately 30% to 40% of pregnan ...
after the 28th week. The subsequent ''
Planned Parenthood v. Casey ''Planned Parenthood v. Casey'', 505 U.S. 833 (1992), was a landmark case of the Supreme Court of the United States in which the Court upheld the right to have an abortion as established by the "essential holding" of ''Roe v. Wade'' (1973) and is ...
'' (1992) modified the "trimester framework", permitting the states to regulate abortion in ways not posing an " undue burden" on the right of the mother to an abortion at any point before viability; on account of technological developments between 1973 and 1992, viability itself was legally dissociated from the hard line of 28 weeks, leaving the point at which "undue burdens" were permissible variable depending on the technology of the time and the judgement of the state legislatures.


Born-Alive Infants Protection Act of 2002

In 2002, the U.S. government enacted the Born-Alive Infants Protection Act. Whereas a fetus may be ''viable'' or not ''viable'' in utero, this law provides a legal definition for personal human life when not in utero. It defines "born alive" as "the complete expulsion or extraction from his or her mother of that member, at any stage of development, who after such expulsion or extraction breathes or has a beating heart, pulsation of the umbilical cord, or definite movement of voluntary muscles" and specifies that any of these is the action of a living human person. While the implications of this law for defining viability in medicine may not be fully explored, in practice doctors and nurses are advised not to resuscitate such persons with gestational age of 22 weeks or less, under 400 g weight, with
anencephaly Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fai ...
, or with a confirmed diagnosis of trisomy 13 or 18.


U.S. state laws

Forty-three states have laws banning post-viability abortions unless pregnancy threatens the life or health of the woman or there is a fetal abnormality. Some allow doctors to decide for themselves if the fetus is viable. Some require doctors to perform tests to prove a fetus is pre-viable and require multiple doctors to certify the findings. The procedure intact dilation and extraction (IDX) became a focal point in the abortion debate, based on the belief that it is used mainly post-viability. IDX was made illegal in most circumstances by the
Partial-Birth Abortion Ban Act The Partial-Birth Abortion Ban Act of 2003 (, ,
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in 2003, which the U.S. Supreme Court upheld in the case of ''
Gonzales v. Carhart ''Gonzales v. Carhart'', 550 U.S. 124 (2007), was a landmark decision of the U.S. Supreme Court that upheld the Partial-Birth Abortion Ban Act of 2003. The case reached the high court after U.S. Attorney General, Alberto Gonzales, appealed a rul ...
''.


Limit of viability

The limit of viability is the gestational age at which a prematurely born fetus/ infant has a 50% chance of long-term survival outside its mother's womb. With the support of neonatal intensive care units, the limit of viability in the developed world has declined since the 1960s. 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. 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 A world record is usually the best global and most important performance that is ever recorded and officially verified in a specific skill, sport, or other kind of activity. The book ''Guinness World Records'' and other world records organization ...
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 Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between ...
, 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).


Factors that influence the chance of survival

There are several factors that affect the chance of survival of the baby. Two notable factors are age and weight. The baby's gestational age (number of completed weeks of pregnancy) at the time of birth and the baby's weight (also a measure of growth) influence whether the baby will survive. Another major factor is gender: male infants have a slightly higher risk of dying than female infants, for which various explanations have been proposed. 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.


See also

*
Beginning of human personhood The beginning of human personhood is the moment when a human is first recognized as a person. There are differences of opinion as to the precise time when human personhood begins and the nature of that status. The issue arises in a number of f ...
* Futile medical care * Office for Human Research Protections#Additional protection for pregnant women, human fetuses, and neonates


References


Further reading

* {{DEFAULTSORT:Viability (Fetal) Neonatology Childhood United States abortion case law Right to abortion under the United States Constitution History of women's rights in the United States