Roe vs Wade is no longer the ruling case in abortion law. Planned Parenthood vs Casey got rid of the trimester basis for setting the legality of abortion and replaced it with “viability.”
Under Roe vs Wade, states couldn’t interfere with abortion for the first trimester (12 weeks) but were allowed to regulate for the health of the mother during the 2nd trimester. States could forbid abortion in the last trimester.
Under Casey, the “[T]he State has legitimate interests from the outset of pregnancy in protecting the health of the woman and the life of the fetus that may become a child.” And, under Casey, states could ban abortion of a viable fetus — IOW, one that could survive outside the womb.
There have been recent examples of 22 week fetuses surviving outside the womb, so, under Casey, states can ban abortion after 22 weeks of pregnancy.
When Casey was decided, viability was 24 weeks. So there was no major difference between the Roe vs Wade standard and the Casey standard, except that Casey allowed health regulation from the onset of pregnancy rather than at 2nd trimester.
Now that viability is, arguably, 22 weeks, the anti-abortion folks want to roll back the viability standard and set 20 weeks as the limit to legal abortion. At that fetal age, it would be easy to underestimate the stage of pregnancy and perform a (now) criminal abortion. Also, it would so narrow the window of opportunity that many or most abortions would be foreclosed by time.
Given legal precedent, the anti-abortion folks have a good shot at winning this.