Just for fun.

It's rare I get to use any of the knowledge I gained in school anymore. So I was thinking about this on the long drive to and from the hospital. Kurt and I are both type O+. Kurt only knows that his parents are also both O+. Mine are O+ and A+, but I also know I have an O- sister. That gives me a 67% plausibility of being heterozygous, a carrier for the negative gene (25% probability my parents would produce a -- child, 25% probability of ++, and 50% probability of +-, for a total of 75% phenotypically +. We know I'm positive, so of the 75%, 67% are heterozygous.) Since Kurt doesn't know of any Rh- types in his family, I used the probability for the population. Roughly 15% of the US population is Rh-. I rounded to 16% because it makes the math infinitely easier. We can assume Hardy-Weinberg equilibrium for the population with regard to blood type, so the frequency of the + and - alleles are .6 and .4 respectively (square root of .16 is .4, 1-.4=.6) Frequency of heterozygotes would be 2*.4*.6=.48. We know Kurt is phenotypically +, so the plausibility of his being heterozygous is .48/(.48+.36)=.57. Sooooooo, with what we know, the probability of our having an Rh- child would be .57*.67*.5=.19, 19%, only a little bit more likely than the population at large. It turns out Quinn is O-, which was a bit unexpected, but now we know for sure that we are both heterozygous, and we now have a 25% probability of producing an Rh- child. I'm not sure if I did that all right. I got home and looked up in one of my text books, but couldn't find exactly what I was looking for. Anyone want to check my math?

Another thing I've been thinking a lot about lately is whether Quinn came at his original due date or not. I was briefly pregnant last summer, and miscarried just before 6 weeks. My due date would have been April 6. Quinn was born April 4. That's a bit creepy to me. I wonder if some part of him has been with me for 9 months afterall. What's even creepier is that we had really been hoping for a spring baby. Dorian's birthday is July 2, so we already had a summer baby. I didn't want to be pregnant in summer again. Faith's birthday is February 26, and where we are, that is still deep winter. It was hard to bundle up 2 kids to do anything, so I didn't want another winter baby. We thought spring would be ideal. Be careful what you wish for.