Fetal viability

Fetal viability or foetal viability is the ability of a fetus to survive outside the uterus. Fetal viability or foetal viability is the ability of a fetus to survive outside the uterus. Viability, as the word has been used in 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 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.' 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.' There is no sharp limit of development, gestational age, or weight at which a human fetus automatically becomes viable. According to studies between 2003 and 2005, 20 to 35 percent of babies born at 24 weeks of gestation survive, while 50 to 70 percent of babies born at 25 weeks, and more than 90 percent born at 26 to 27 weeks, survive. It is rare for a baby weighing less than 500 g (17.6 ounces) to survive. The chances of a fetus surviving increase 3-4% per day between 23 and 24 weeks of gestation and about 2-3% 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. The period of viability refers (traditionally) to the period after the twenty-eighth week, or more recently the twenty-fourth week, of gestation when a human fetus is capable of living outside of the womb. Whether the fetus is in the period of viability has legal ramifications as far as the fetus' rights of protection are concerned. It sometimes incorporates weight as well as gestational age. The United States Supreme Court stated in Roe v. Wade (1973) that viability (i.e., the 'interim point at which the fetus becomes ... potentially able to live outside the mother's womb, albeit with artificial aid') '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 preserving potential life became possibly controlling, permitting states to freely regulate and even ban abortion after the 28th week. The subsequent Planned Parenthood v. Casey (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 judgment of the state legislatures. 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, or with a confirmed diagnosis of trisomy 13 or 18.