I have 2 bipolar friends. Both want kids but are afraid to have them for the same reason. Perhaps adoption is an answer. I had an aunt and uncle who didn't know they had the gene for cystic fibrosis. They had 5 children of which 4 had cystic fibrosis. They all died before they were 30. It was hard on them as you would have expected but they never regretted having the kids. Each one had purpose and meaning and touched other people. Your child could be spared the gene or could be controlled with meds. Regardless, your child could make a difference in the world. If we reproduced only if we had perfect genes, we would never have had the great brains of Stephen Hawking or John Forbes Nash, Jr.
I say if you are fairly under control and are up for the possible challenge, have the baby, love your child, and embrace whatever imperfections they have. No one is perfect. Motherhood is the hardest job I ever had and the one I loved the most.