When to try for a second child after having a preemie?

Hello. I am just wondering when you guys decided to start trying fir a second child. Our first daughter was born at 33 weeks 5 days weighing 3 pounds 8 ounces and had a 17 NICU stay, surgery at 2 months old, and has now at 15 months been diagnosed with pediatric asthma. The reason she cane early is because I have chronic high blood pressure, that turned into preeclampsia. Pretty much we knew that it would from day one but just didnt know when. Also, when I had my daughter via emergency c section, my placenta was dead due to blood clots from a blood clotting disease I have that we were unaware of. With all of that being said, my doctor said it will be okay for us to have another child its just very high risk, which of course we know that all too well. We know to expect an early baby, its just a bery scary thing. However we would LOVE to have another child, we just want some insight from non family members on what they think. Thanks a bunch in advance!