SART Statistics and Egg Freezing

Every year, the CDC collects data from IVF clinics on the success rate of various ART (Assisted Reproductive Technology) procedures and reports that data on its website. The data is also reported on the SART (Society for Assisted Reproductive Technology) website in a format that may be easier to read. By comparing the reports for different clinics, you can see which have the highest success rates. SART warns that “Patient characteristics vary among programs; therefore, these data should not be used for comparing clinics,” but many people believe that in fact comparing success rates amongst clinics is a valid idea. You can also compare a clinic’s success rate against the national average to see if your clinic is above average or not. Carole Wegner points out in her “Finding a Good IVF Clinic” post, “I wouldn’t go to a worse than average clinic. Would you?”

The only problem for us egg freezers is that the CDC and SART don’t publish data on egg freezing. However we can still benefit from the reports. Common sense says that if you have a clinic that is great at other IVF procedures, they are more likely to be good at egg freezing than a clinic that is only mediocre at other IVF procedures.

In her “Finding a good egg freezing clinic” post, Wegner mentions finding a clinic that has a good success rate for regular IVF for the <35 age group. That would be “fresh embryos from non-donor oocytes” in SART language. But the reports also contain information on a couple of procedures that involve freezing and thawing: “thawed embryos from non-donor oocytes” and “thawed embryos from donor oocytes.” I wonder if looking at those numbers might be more meaningful for the case of egg freezing, because at least they have to do with freezing and thawing things--even if those things are embryos rather than eggs.

So here’s where things get confusing: of the four clinics I’m considering, the one that has the lowest success rate for transfers of fresh embryos has the highest success rate for transfers of frozen embryos. The one that has the second-highest success rate for transfers of fresh embryos has the lowest success rate for transfers of frozen embryos. How am I supposed to interpret this? If anyone has suggestions, please let me know in the comments!