I have been bipolar since I was 18, but was treated for anorexia and depression and the bipolar remained undiagnosed until 2 yrs ago. I went through two pregnancies that were stable, only my depression was a problem at times. Afterwards I amazingly had no postpartum, but I think I was actually slightly manic. My sons are now 13 & 15 and my 15 yr old is also bipolar. I am now married to a new man and he wants a baby but understands that I am terrified of going off my meds or of having another child with bipolar, my younger son is fine. But I think if you work very closely with your doctors, remain in therapy and are very in tune to your emotions, you can have a baby.
Worse case scenario is you have a manic episode or become depressed - you will be being monitored. It is temporary - 9 months - and then you go right back on your meds. Just my opinion - good luck.