1st trimester yes(This is not a baby, this is a mass of cells. This would be similar to aborting your arm or your eye.)
2nd trimester...eh (Gets iffy in here. If it was not the mothers choice to have it, aka rape or incest, or if it will be detrimental to the mother's health, aka early teen mother, go for it. Otherwise you f*cked up, live with it. "But the condom broke, not my fault." Whaaaaaaambulance. You chose to have sex, you accepted the risks however small they were at the time. Similar to playing Russian roulette with a ten-thousand chambered gun.)
3rd trimester no (read murder)