Aw, I'm so sorry. In all honesty, I hope the baby moves to where it's supposed to, I really do. When it comes to telling your parents, the best thing you can do is... Well, tell them. I mean, it's a grim subject and it will be hard, but there's not really anything you can do at this point and there's no use in sugar coating things. It's not as if you willed the child to attach itself there or can help it for that matter. Sometimes things, as unfortunate as it is, happen that way, and it isn't fair.
If the baby does have to be removed, you really shouldn't feel like it's your fault. You have to take your health into consideration, too. I believe your parents will understand that. It's not as if you're deciding you don't want the baby or are getting it removed for an irresponsible reason. You also have to look at the fact that if it's not done, you both lose your life. What effect would that have on your family? It's better to save one than lose both. You can't help that this happened, it's not your fault.
I really wish you the best of luck. :c
I hope things work out for the best, I'm sure we all do.