To add on, as long as sex education and reproductive care (gynecology, pregnancy tests, contraception, abortion) are freely available, there's no *need* to do 3rd trimester abortions on healthy fetuses. Most women notice they're pregnant pretty early on and can make that decision early. 

3rd trimester abortions aren't capricious "yeah like I changed my mind" decisions, they're terrible tragedies where a wanted and hoped-for fetus is dead and rotting and has to be removed before the mother gets septicemia, or lacks a brain or a heart or is otherwise non-viable.