IVF With Blastocyst Transfer

A fertilized egg grows rapidly progressing from 2 cells on day 1, to 4 cells on day 2, 8 cells on day 3 and becomes a blastocyst on day 5. Traditional IVF transfer of embryos usually takes place 3 days after fertilization. Recent advances allow us to successfully transfer embryos at day 5, but to what benefit and trade-off.

The benefit to a blastocyst transfer is that implantation rates are higher. This is likely because of two reasons. The transfer timing is more physiological (at day 2 the embryo is in the fallopian tube) and the embryo is likely healthier than the average day 2 transfer, since it has already proven to survive 5 days.

Therefore, when we used to transfer 3-5 embryos at day 3, we had no idea as to how many of them would make it to day 5, or make it to a live birth. Potentially, all embryos could survive and the result would be quadruplets or quintuplets. Today, we can see that if all embryos make it to day 5, we shouldn't transfer all the embryos. The risk of multiple births would skyrocket if we did. Similarly, the risks of multiple births, especially higher order multiple births, should decline if we only transfer two to three healthy blastocysts, while maintaining our pregnancy rates.

On the downside, it is possible to have few or no embryos survive to day 5 to transfer. It is unknown whether those embryos would have survived beyond the day 3 transfer either. But, if they were transferred at day 3, at least we would have a chance of conceiving.

We currently offer Blastocyst Transfer to all patients who have at least 10 fertilized eggs. We will decide together which option is best for each couple.