Good, voluntary makes the blood safer I imagine. It's good that you are a negative. (Probably the only negative thing about you.) It also means less danger of Rhesus Factor problems ... negative means the absence of the Rhesus Factor. Your babies are safe if your baby mommy is negative or positive. But if you were Rh+ and your baby mommy was Rh-, it can lead to problems.

For hubski readers, here's my understanding of the Rh factor story:

Because I was Rh-, and my baby's daddy was Rh+, I had to take some a treatment at five months that would prevent complications. My understanding is this: in an Rh- mother and an Rh+ father, the antibodies to the Rh+ factor multiply with each successive baby. Consequently the lblood of my youngest brother (youngest of five) was at war with the antibodies in my mother's blood, and when he was born, he required a complete blood transfusion. But that was in 1960. Now if there might be an Rh-/+ issue, the mother is given a treatment to reduce the possibility of Rh-related complications. I'll check Wikipedia at some point, or maybe someone else will.