In the second trimester, doctors typically conduct a number of prenatal screening tests that can detect a variety of different chromosomal and congenital conditions. The conditions being screened for can vary heavily in their prognosis. Children with some of these conditions, such as Down syndrome and mild to moderate neural tube defects, can be born alive and live a regular lifespan -- although they may have developmental, physical, or cognitive disabilities.
Other conditions detected in prenatal screening can be fatal or can have a profoundly poor prognosis. In anencephaly, for example, half of babies with the condition will not survive birth and the other half die within hours or days. Chromosomal condition such as trisomy 13 and trisomy 18 can result in a baby with a short lifespan; 90% of babies with either of these conditions do not survive past age 1, and during their lives are frequently afflicted with health problems and medical interventions.
When prenatal screening and subsequent diagnostic tests return a definitive verdict of a condition with a less than optimal prognosis, parents may face the decision of whether or not to continue the pregnancy. These terminations are sometimes called medically based or medically indicated termination.
Parents may also end up considering a medically based termination when rare pregnancy or other health complications pose a notable threat to the mother's life if she continues the pregnancy.
When parents choose to terminate a pregnancy because of severe medical conditions in the baby, the medical procedure is technically a second-trimester abortion or a "late-term" abortion -- and it is technically elective because parents can choose whether to let nature take its course or to end the pregnancy. As opposed to most elective terminations, however, most babies aborted late in pregnancy for medical reasons were very much wanted and the parents may deeply grieve the loss of the baby.
Abortion of any type tends to be a divisive and emotional issue, both personally and politically. People who are philosophically or religiously opposed to abortion may view all abortions as wrong -- no matter the circumstances. Activist groups are sometimes deeply opposed to these medically based terminations, and numerous online sites make a case that every baby should be brought to term. People who have a pro-choice stance usually have no objections to medically based terminations.
Looking more importantly at the feelings of the parents, most people fall somewhere on a spectrum. Some cannot fathom the idea of having a late-term abortion at all even after a diagnosis of fatal birth defects, while others wrestle with the idea but ultimately opt for the termination, and still others do not struggle with the decision even though they grieve the loss of the baby.
In cases when the condition being diagnosed is not fatal, some opponents to selective abortion after a prenatal diagnosis have fears that parents may not receive full information. Outcomes have improved over the years for some conditions, such as Down syndrome, and they fear that parents may receive an inaccurate and dismal view of what it is like to raise a child with a physical or developmental disability.