Bipolar and Schizophrenic mother in law

I wouldn’t normally post something like this on the internet but I am just reaching out for any stories of anyone in a similar boat. I am with my soulmate. A second marriage for me at the age of 40. He’s 36 with no kids. I have 2 boys from my marriage who are 11 and 7 years of age. They definitely keep us busy as we don’t have much family help at all here in Dallas. My concern is that my mother in law (whom I haven’t met) is a bipolar and schizophrenic who is in and out of the psych ward. She has been sick since my fiancé was 4 years old so much of his life she has been hospitalized and never has really been able to work. My concern is that I’m dying to have a child with him. He would love a child together as well outside of the boys. I’m so scared that our baby will have the same condition that his mom has. I’ve researched and googled but it seems it’s a possibility but could possibly skip the baby. Anyone in a similar boat or have a perfectly healthy child in this scenario. We talked about trying soooon and this is heavily on my mind. Thanks guys