In IVF, when is a transfer typically performed for a blastocyst-stage embryo?

• A. Day 1
• B. Day 3
• C. Day 5
• D. Day 7

Answer: (C)

The key idea is that transfer timing follows embryo development stage. A blastocyst forms about five days after fertilization, so transferring on day five aligns with the embryo reaching the blastocyst stage and with the uterus being most receptive to implantation. Culturing to day five allows selection of embryos that have shown robust development, which typically leads to higher implantation and pregnancy rates than transferring earlier at day one or day three when the embryo is still in the cleavage stage. Day seven is less common and may indicate slower-growing embryos with potentially lower success, while day one or day three transfers miss the blastocyst stage altogether. Therefore, the typical transfer for a blastocyst-stage embryo is around day five.