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Freezing and thawing blastocyst stage embryos can be tricky. That's why I qualified my reply to your post by saying "laboratories that routinely freeze embryos at the blastocyst stage". I don't know what method CCRM is using for blastocyst freezing or how often they freeze blastocysts. Both of these factors could contribute to a 60% survival rate. Also, make sure they were talking about survival of blastocysts, not Day 3 embryos or embryos overall. On the up side, CCRM has a good term delivery rate for frozen-thawed embryos. So the embryos that do survive have good developmental potential.
A word about interpretation of pregnancy rates:
Although CCRM has a relatively high pregnancy rate (higher than the national average), they achieve this by transferring around 3 embryos. This results in an unacceptable level of high order multiple gestations (triplets and higher) in all age categories (up to 10% of their pregnancies are triplets and higher). Triplets, quads etc. are frowned upon in the IVF community as they are high risk pregnancies that endanger the babies and the mom. Triplets are always born very prematurely and can have multiple long term health problems assocoated with pre-term delivery. Read between the lines. Because pregnancy rates are an "all or none" end point, they can be misleading.
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