Saturday, July 09, 2022

Why transferring more than 1 embryo reduces pregnancy rates. More is not always better !


Many IVF clinics routinely transfer two or three or four embryos at a time to inflate their success rates, and often patients push their doctor to transfer more embryos because they think that transferring more embryos will increase their chances of having a baby.

This is actually very short sighted , and let me explain why .

While it’s true that transferring two embryos in one cycle has a higher pregnancy rate than transferring a single embryo in that cycle , this is actually comparing apples and oranges. Let’s suppose you have two top quality blastocysts. If you transfer both and don’t get pregnant, you need to start a fresh cycle , which is expensive and stressful . On the other hand, if you transfer one and freeze the other , you can then use the frozen embryo for your next attempt in case the first one fails, which is much less expensive. And if you do get pregnant with the transfer of a single embryo, you can keep your frozen embryo for your second baby ! This is why we tell patients that it's much more sensible and cost effective to transfer only one embryo at a time, because we are not wasting the spare embryos – we are freezing and storing them for you , and the success rate of freezing and thawing embryos is nearly 100% in a good clinic , thanks to the science of vitrification. In fact, the embryo implantation rate is higher with frozen embryos, because we can prepare the endometrium better, so that it’s receptivity is optimal.

Now if you transfer two embryos and both implant , you might think that this is a great outcome, because you have created an instant family, and got a bonus in the bargain – two babies for the price of one !

This is actually not true, because the complication rate with a multiple pregnancy is much higher than with a singleton pregnancy . You run the risk of miscarriage , and the chances of preterm labour are increased considerably, which means these premmies will often end up in a NICU ( Neonatal Intensive Care Unit ). They will often have lifelong problems because they were so small when they were born , and the biggest tragedy is that this is an iatrogenic problem – one created as a result of medical care, by transferring more than one embryo at a time.

When you need to decide whether you should transfer two embryos at a time with transferring a single embryo, you should compare the live birth rate with two embryos at one time with a single embryo at a time in two consecutive cycles . The cumulative ( overall) conception rate  with transferring 1 embryo and freezing the other one is actually better because freezing embryos has become a standardized process, and the implantation rates are higher in a frozen  cycle because it’s possible for us to prepare the endometrium  so it's optimally receptive.

If your doctors insists you transfer more than one embryo, this is a red flag, because this suggests he doesn't have enough confidence in the quality of the embryos his IVF lab creates. The best way to check the quality of your embryos is to demand by demanding photos of your embryos. This is standard clinical practice, and something which all good clinics all over the world do routinely and proactively. Remember that more is not always better !

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