A clinic uses a made-up model for learning…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A clinic uses a made-up model for learning. Two embryos are transferred. Each has a chance of of implanting, and the two do not affect each other. The counsellor lists every outcome of the two embryos to find the chances.
- What is the chance that at least one embryo implants, in per cent?
- What is the chance that both implant, in per cent?
- What is the expected number of embryos that implant?
- The counsellor says that adding a third embryo raises the chance of a pregnancy, and also another chance. Which chance is that?
Need a reminder? The key ideaShow
In IVF, ZIFT and ICSI, the gametes meet in a dish. In GIFT, AI and IUI, they meet in the body of the woman. A zygote or an embryo of up to blastomeres goes into the fallopian tube, and a larger one goes into the uterus. If each of embryos implants with chance , on its own, the chance of none is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. for each of embryos.
Plan. List every outcome, with its chance.
Step 1. The outcomes. Neither: . Only the first: . Only the second: . Both: . The total is .
Step 2. At least one. .
Step 3. Both. .
Step 4. The expected number. embryos.
Step 5. The third embryo. It also raises the chance of two or more implanting, which means a twin or a triplet pregnancy.
Answer: ; ; embryos; the chance of a multiple pregnancy.
Check. The chance of at least one, , is a little less than the sum of the chances, .
Watch out. The chance for one embryo in real life changes with the age of the woman and the quality of the embryo. These numbers only teach the method of counting.
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