Pregnancy is tricky. Birth is difficult. Each mother and child are unique and can possibly have an array of health complications that are difficult to interpret. Therefore viability for one child may be different than for another. However most people agree that by end of the second trimester the entity with a beating heart inside the womb is, at a minimum, close to full personhood.
Approximately 1.3% of abortions are later abortions at or after 21 weeks. This amounts to anywhere between 8,000 and 15,000 or more a year. (Who Seeks Abortion at or After 20 Weeks? Wiley Online Library. 4 November, 2013. https://doi.org/10.1363/4521013.) Roe v. Wade allows states to prohibit third trimester abortions as long as there are exceptions for the life and health of the mother.
Many pro-lifers speak disparagingly about the “health of the mother” exception, saying that it is a loophole. They argue that any woman wanting a late-term abortion can simply claim she has a mental health problem. This kind of claim is difficult to disprove conclusively. Therefore third trimester bans have little force.
It seems to me, however, that any woman seeking a later term abortion really is suffering from a severe mental health problem. Healthy women do not want to hurt their babies. This desire to kill a large baby in utero should be considered a health emergency. A woman in this situation should be treated with compassion. Once it is determined the baby can survive outside the womb, the woman should be permitted to end her pregnancy prematurely through induced birth or c section with the choice of being unconscious for the experience.