Ugh! R's dad got to show me up last night at dinner. He was saying that ABO incompatibility was an issue between mother and child, and when I disagreed he just steamrolled me with problems that came up in his experiences with having kids. It turns out he was talking about ABO hemolytic disease of the newborn, rather than ABO incompatibility. I had just never heard of this issue and it had been a while since I studied blood types, so I couldn't correct him. Nevertheless, I have a degree in biology! I should have known about this! Of course, I haven't actually had a sex ed. class since 6th grade, nor did any of my college classes deal with human reproduction, so I suppose the gap in my knowledge isn't unforgivable. This also isn't something that would come up in the family lore, as we are all type O and therefore have never experienced this problem. R's dad only learned about it after he had kids. I swear, it seems lot people don't advertise about reproduction. Don't want to scare off prospective parents, I suppose.
Of course, I'm never going to be able to say my response to him, as bringing it up later with the express purpose of demonstrating his factual errors would make me seem petty and insecure (and perhaps I am, in some areas). Nevertheless, I need to say this somewhere because it is eating me alive, so here is my rebuke:
"Tripping my sorry ass up by using the wrong name for a physiological problems doesn't make me wrong. I may not have known about ABO hemolytic disease of the newborn, but I was correct when I denied that ABO incompatibility was the issue. The placenta is there to keep ABO incompatibility from being an issue. In any case, R and I are not the same as you and your wife, if we look at it purely based on genetics, even though phenotypically we are the same. Given that all your children wound up with A-type blood, I'm going to guess that you are of the AA genotype (Yes, I know that getting all of one type or all of another is equally probable if you were AO, seeing as each child would individually has a 50-50 chance of being type A or O. Nevertheless, on average half of your children would be type O). In any case, being a product of you and your O-type wife, R is definitely AO genotype. R and my children therefore only have a 50-50 shot of having A-type blood, nor is that a guarantee of ABO HDN, so don't tell me that all my children after my first will have to go under the light. It could happen with my first child or (more likely) not even happen at all."