Fetal Viability

A cheat sheet for the news.
May 25 1997 3:30 AM

Fetal Viability

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"Viability" has become the focus of the abortion debate. Last week, the Senate rejected Majority Leader Tom Daschle's bill banning the abortion of "viable fetuses." But William Bennett and William Safire hailed Daschle's bill as the great compromise that might settle a quarter century of arguments about abortion. Forty-one states already restrict the abortion of viable fetuses. What is a viable fetus? How is the concept of viability relevant to the moral and legal issues of abortion?

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Roe vs. Wade, the 1973 case legalizing abortion, made fetal viability an important legal concept. The Supreme Court ruled that states cannot put the interests of a fetus ahead of the interests of the pregnant woman until the fetus is "viable." The court defined viable to mean capable of prolonged life outside the mother's womb. It said this included fetuses that doctors expected to be sustained by respirators. The court accepted the conventional medical wisdom that a fetus becomes viable at the start of the last third of a pregnancy, the third trimester, sometime between the 24th and 28th week (a pregnancy usually lasts 38 weeks). Because the point of viability varies, the court ruled, it could only be determined case by case and by the woman's own doctor. Even if the fetus is viable, the court said, states could not outlaw an abortion if the woman's life or health was at stake.

Justice Sandra Day O'Connor argued in a 1983 decision that Roe was on a "collision course with itself." She said that improvements in technology would continually push the point of fetal viability closer to the beginning of the pregnancy, allowing states greater opportunity to regulate the right to an abortion. And this seems to be the case--up to a point. Doctors now believe a fetus can become viable during the 23rd week--a week earlier than was thought 24 years ago. Most hospitals will only perform abortions through the 22nd week of pregnancy.

But no baby has ever been successfully delivered before the middle of the 22nd week. Babies delivered during the 22nd and 23rd weeks weigh just over a pound. Their lungs have barely formed and their airways are not developed enough to inhale. Circulation depends on the use of ventilators and injections of hormones. A baby born during the 22nd week has a 14.8 percent chance of survival. And about half of these survivors are brain-damaged, either by lack of oxygen (from poor initial respiration) or too much oxygen (from the ventilator). Neonatologists predict that no baby will ever be viable before the 22nd week, because before then the lungs are not fully formed.

Probability of survival increases for babies born later in pregnancy: 25 percent in the 23rd week, 42 percent in the 24th week, 57 percent in 25th week. By the 30th week, when a newborn doesn't require a ventilator to breathe, it has a 90 percent chance of survival. And only after the 30th week do the risks of long-term brain damage begin to substantially subside. Because premature babies depend on technology, survival rates vary based on access to that technology. For instance, in rural communities, which commonly lack expensive infant intensive-care units, survival rates in these early weeks are much lower.

Doctors assess a fetus's viability by attempting to guess whether its lungs have formed. Sonograms allow doctors to estimate the fetus's weight, which correlates with the lungs' development, and to look for signs--such as the development of functioning eyelids and creases in the skin--that coincide with the onset of a functioning respiratory system. None of the methods for predicting viability are very precise.

Despite important Supreme Court decisions since 1973 modifying the doctrine of Roe, the court's thinking about fetal viability has remained fairly constant. The only significant revision came in the Casey decision (1992), which made viability even more important. The court said that state laws could require a woman and her doctor to perform tests to prove that a fetus is not viable before she obtains an abortion.

Forty-one states now have laws restricting post-viability abortions. 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. Eleven states have banned the procedure called intact dilation and extraction (IDE)--also known as partial-birth abortion--in the belief that this procedure is used mainly post-viability.

Banning IDEs nationwide is a major goal of the pro-life movement. Movement adherents claim that the IDE procedure--in which delivery is induced, the fetus's skull is crushed, and its brains are suctioned--amounts to infanticide. Barring this procedure is also the only regulation of abortion that public-opinion polls say has a majority of support. Pro-choicers say the ban on IDEs is inconsistent with Roe, because the procedure can be used to abort pre-viable fetuses.

Some medical ethicists and constitutional scholars say that the Supreme Court was wrong to create the pre-viability/post-viability distinction in the first place. Why, they ask, does the fact that a fetus can survive outside the womb with the help of vast medical technology change either of the interests at war in the abortion debate: the fetus's own claim to "human-ness" and a woman's right to control her body? Even if viability is an important moral line, is it drawn in the right place? Keeping alive a baby born in the 22nd week costs several hundred thousand dollars and usually fails, regardless of the effort.

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