I don't think that the fear is irrational. I don't know too much about the genetics of MI, but if I had a do-over, I wouldn't have had children (I was not diagnosed with depression until much later in life, and my son has it) I wouldn't wish this on anyone. Perhaps by the time you are ready to have children, treatment for MI will have improved.

Pregnancy is, in itself, much like raindropvampire says....we are human incubators.
But if you actively trying to conceive, then it doesn't matter to you. You focus on the fact that you're creating a life.

Delivery is hard. Uterine contractions are like cramps times a thousand. They get closer and closer together until they blend one into another.
When it's time to push, you feel pain and the pressure of the baby coming out. Nothing distinguishable.
This is with no drugs.

It really all boils down to the end result being worth the pain.

Post-partum depression hits some women hard (me). It's like the sadness of PMS times a thousand......you just have to watch the news to see how bad it can be (those are extreme cases, of course). Some women have no problems.

Just my opinion.