Its just a pointless meaningless question. Abortion being made illegal or difficult doesnt happen in a vaccuum. You could say “if we made abortion illegal then women would stop sleeping around” but you cant make abortion illegal in the west. It will not happen anytime soon, and if it did happen, it would only be in response to a large cultural and social change in the first place that would already be less ok with womens irresponsible unprotected sex.
But even if it could happen all of a sudden, it wouldnt matter. When abortion was illegal in america unprotected sex did not happen less and pregnancy rates did not drop. Many women performed abortions on themself or they used unlicensed doctors and dangerous methods. Obviously, the law did not stop women sleeping around and it doesnt even stop abortions from happening. It just switched the safe abortions to unsafe ones and fueled a market for illegal abortions.
And this is all talking about the women. What about the children born to irresponsible women who cant or wont get an abortion? Those children are not going to be treated well and it is not fair to them to be forced in that situation just because of an idea eith no evidence behind it that making abortion illegal would stop women from whoring around.