Most people don't realize it, but abortion is legal through the entirety of a woman's pregnancy. Greg Koukl explains it this way:
"In Roe v. Wade, the Supreme Court struck down a Texas statute that prohibited abortion. In the decision, the Supreme Court said states may not prohibit abortion in any way in the first trimester, that they may only regulate abortion in the second trimester for the purpose of protecting maternal health, and that in the third trimester, the state may “regulate, and even proscribe, abortion” except when it is necessary to protect the life and health of the mother. That last phrase is the most important phrase, however, because the Court defined health in Doe v. Bolton (Roe's companion case) to include “all factors - physical, emotional, psychological, familial, and the woman's age - relevant to the wellbeing of the patient.” Chief Justice Burger added that the definition of health used must be "in its broadest medical context."
The end result is that any reason given for abortion can be construed as a health risk to the mother and therefore abortion in the third trimester is easily justified in practice. In so many words, the court decided that states could not prohibit abortion in any significant way up until the moment of birth. Not only is this the opinion of many legal scholars (references available on request) but is the fact of the matter in America today. Roe v. Wade was reaffirmed in this holding (although with a new grounding) in Planned Parenthood v. Casey in 1992. Under those decisions, many abortion providers advertise third trimester abortions for fetal abnormalities. Dr. Hern is one with a prominent internet presence who does abortion long after fetal viability, acknowledging he can only perform abortion if continuing the pregnancy will be adverse to the mother's health. What definition of health? Undoubtedly, the definition found in Doe v. Bolton."
Here's Dr. Hern advertising legal, third-trimester abortions after 26 weeks. To learn more about third-trimester abortion in America, please read this!