I had a dream about my sister (who is pregnant) cutting her stomach open and tying her baby to a pole and strangling it. Then the baby transformed into my niece, (my other sister's daughter). It was pretty scary.. any idea?

Well a dream about pregnancy normally means 4 things:
1)A Process or project somewhere in your life.
2)Responsibility for another person, animal, etc.Somehow in your life
3)Responsibility for self or for your inner child
4) Curious about pregnancy
Death has reasons for dreaming it:
Usually means someone is insecure about something and in your case (in your dream) It may have meant that your sister was unsure if she was pregnant and didn't want anyone to find out? Just some suggestions.. I hope it helps in some way x