The Gambler

I was keeping it together pretty well until the last few days of the 2ww. For the uninitiated, that's the two week wait between ovulation/transfer and pregnancy test. For my IUI's I don't remember getting really stressed during the 2ww, just being disappointed when the dreaded period arrived. Initially this time, work was a wonderful distraction. By day 9, however, the realization that this was truly the last option before adoption, and the fear of having to start all over again with a big box o' drugs, began to eat at me.

So, I spent an inordinate amount of time trying to calculate the probability that I would end up with 1 implanted embryo. At my age and at UCSF, the probability of any transferred embryo implanting is 22%. 3 were implanted. I taught stats in college as part of a population biology class, and sadly don't remember anything useful. So, I had to resort to the source of knowledge and truth, the internets. At first, it seemed simple. If each embryo is an "independent event", then don't you just add the probabilities? 22% + 22% + 22% = 66% probability that I would get 1 implanted embryo. Well, no, because if you have 3 coin flips, and are looking for 1 heads: 50% + 50% + 50% = 150%. You can't have 150% probability. I found this formula, which looked fabulously simple:
P(A or B) = P(A) + P(B) - P(A and B) - in words, the probability of A or B happening is the probability of A happening, plus probability of B happening, minus the probability of A and B happening. Until I realized I needed to know the probability of A and B happening. This apparently requires logarithms and other things that are truly beyond my ken.

So I had to resort to gambling. Having spent a few long nights at the craps table in Vegas, I felt quite comfortable with this fine and practical application of probability. This gambling table was perfect. Check out section 2, The Fundamental Table of Gambling (FTG). I was somewhere close to, probably over, 60% probability of 1 embryo implanting.

Great! But then I remembered that I'm only 1 person, and probabilities apply to populations. Boo.