That is the major flaw in Roe v. Wade. They just made up the trimester thing on the fly. The truth is that there have been great advances since Roe was decided, and the day will come when a fertilized egg can be removed safely from a woman's womb, placed into an artificial womb and then go to full term. Does this mean Roe will be its own demise? Quite possibly.

My own view is that abortion rights should be viewed most liberally from the time of conception, and more and more narrowly from that time through birth.