parents don't like fiance

It's terrible that your parents made you have an abortion. But I guess that's not the here and now. I can see why they don't like him for getting you pregnant. But it does take two to have sex (unless it's abuse of course.)

It is going to affect your marriage. The in-laws of both sides are going to be somewhat involved no matter how hard you try to keep them out. If they don't like him, of course they are going to be upset and will probably try to make you leave him. There is no way you can keep forever the fact that you are (going to be) married to him, so you should probably tell them, but you will need to assure them that you want this, you are a big girl now, and it is your decision. You will also need to be sure to tell them that you are not going to be dependent upon them for anything and are going to do this on your own. Only children sneak behind their mother's backs...an adult informs their parents in a mature manner, so that is what you will need to do.

Part of the reason why they may not like is is because no matter your age, they feel responsible for you (and probably always will.)

Parents not liking a chosen partner is not uncommon, but sometimes it isn't a bad idea to try to look a little farther than the "flat out dislike" and see if there really is a good reason for them to not like him. Sometimes it might be a good idea to stop, slow down and take a break and ask yourself if you really want to do what you are doing. I'm not saying that you are making a bad decision or that he isn't for you, I'm just saying that sometimes people tend to rush into things without thinking too much and are too busy to take into consideration how they themselves feel, because they are worried about the negativity of others.

I hope that makes sense. I wish you all the best.