Planning an IVF and have questions? Here is an interview with Rebecca Matthews, PhD, author of IVF: A Patient’s Guide.
Q. Some fertility clinics do embryo transfers 3 days post egg retrieval and others do 5 day blastocyst transfers. Can you please explain the difference between the two, which you prefer, and why?
A. When we stimulate a woman’s ovaries to produce lots of eggs we know that they aren’t all going to grow into viable embryos. Our job is to choose the best ones for transfer that give the highest chance of a pregnancy. One good way to do this is to grow the embryos in the lab for 5 days. In doing so, we can see which embryos stop growing at earlier stages and which embryos are strong enough to make it to the blastocyst stage. These blastocyst embryos have a higher chance of implanting and therefore give us a higher pregnancy rate than embryos transferred on day 3. We prefer to do all our transfers on day 5. Most people still have an embryo transfer even with only a few embryos to start with and it also allows us to put back fewer embryos than we would if we did a day 3 transfer.
Q. How do you help families decide how many embryos to put back on the day of IVF embryo transfer? Have you seen a change over the years of people choosing to put in 1-2 embryos as opposed to 3 or more? What kind of changes do you predict for the future?
A. The decision of how many embryos to transfer is a joint decision between the patient and the doctor. We understand the desire to maximize the chances of success by increasing the number of embryos transferred, but we have to balance this with minimizing the chances of a triplet pregnancy or more. The biggest factor in deciding the number to transfer is the age of the woman. As we get older, our eggs age too and in patients who are in their late thirties and early forties we compensate for this “genetic” aging by increasing the number of embryos we transfer.
In a woman 35 or younger we generally transfer only 2 embryos. On a case by case basis we increase this number according to the age of the woman. There are exceptional cases where we increase the number of embryos transferred above the recommended amount, always with the fully informed consent of the patient, of course. Examples of this could be following a number of previous failed IVF cycles or poor embryo quality on the day of transfer.
In the last few years we are seeing a trend towards reducing the number of embryos transferred. Fertility clinics in the US are not bound by law to operate within certain restrictions like they are in some European countries. While we enjoy this freedom of choice, we have a responsibility to our patients to make the right healthcare decisions by not transferring more embryos than necessary.
In the future we could have the technology to choose only one embryo for everyone. Advanced genetic testing may allow this and researchers are working hard to improve IVF outcomes all the time. For now at least, I am hopeful that the scientific community will work together to share knowledge in order to provide the best available care to everyone.
A. Every day is a gift, whether it is checking the eggs to see if they fertilized, looking on day 5 to see if the embryos grew to blastocyst or finding out someone is pregnant. As embryologists, we understand the importance of our role in the process and the honor it is to be trusted with this important job.