One reason abortion should be legal is women have the right to do what they want in this situation. It is their body and their choice if they even want a child to take care of. Some women might not have the ability to take care of a child in the moment they are pregnant.
Another reason is that most of the public want abortion to be legal. 59% of the public say it should be legal. Only 18% of democrats say that abortion should be illegal. This decision should be based on what the public says. It should not be up to one person's opinion. Also it should be up to the whole country so that it's fair in deciding if abortion should be banned.
A third reason that abortion should be legal is the factor of sexual harassment and rape. 1/5 women are raped, 133 million girls have been sexually harassed, and 35% women are sexually harassed every day. If a woman is raped she should not have to carry a child that reminds her of the events that took place. You can put your baby up for adoption but to carry that child for 9 months, missing work for appointments, and ultimately going into labor is a lot of hard work that some women just can't do.