Again, you are being silly. If there had been ALS in your fathers family, he'd have told your mother, and obviously from your report, there was none in her family, thus, it's sporadic.
In sporadic ALS the chances of two family members getting ALS are absurdly small. You must realize that there are people here on this forum that have lost a parent, sibling, spouse, or are suffering from ALS themselves. And many that KNOW they are living under the cloud of genetic ALSand have watched it descmate their family.
IF your mom has ALS, you all have my deepest sympathies, but there is absolutely no reason to think it is the genetic form. None at all. Now, if you wanted to hold off having a child to. Are for your mother, that I could understand.
I don't know about midwife school, but I'm pretty sure nursing school teaches the basics of how genetic diseases work.