The researchers wanted to see if frozen embryos could develop into blastocysts and be successfully transferred for in vitro fertilization. They compared outcomes of embryos transferred on day 2 or 3 with those transferred on day 5 as blastocysts. They found that transferring blastocysts on day 5 resulted in higher pregnancy rates and implantation rates compared to earlier stage embryos. Blastocyst transfers also had a lower risk of multiple gestations, with most resulting in twins. Overall, allowing cryopreserved embryos to develop into blastocysts before transfer can lead to better outcomes in IVF procedures.