Question for mommies who have had to wean their little one from the early and start formula?

My doctor has highly recommended that I wean my almost 7 month old. I am pregnant again. I am also considered a high risk pregnancy due to a blood clotting disorder I have. In my mind... there have not been enough research to prove that feeding durring pregnancy can send you into early labor. However, there is a small chance that it could. This could mean bad things for me. I could hemorage and die, and/or could lose the baby. I really dont want to take even the smallest chance on any of that, so as of next month, I am going to gradually start switching my daughter to formula. I hate to do it... however, she has had almost 7 good months of milk and I feel I have given her a great immunity boost. Im trying to tell myself its ok. Psychologically, its hard for me. I love feeding and the closeness it brings. So my question is: for any of you moms who have had to wean early or switch to formula, what formula worked best for you and your baby???