How many embryos should be transferred?
I know you can’t see me from where you reading this (or, I hope not; I’m most likely in my pajamas as I type!) but today I am clapping in glee. I love to talk about how many embryos should be transferred! [Think I’m being sarcastic? Ask me sometime and see how long it takes before you try to politely excuse yourself because I won’t stop talking.] For those whose eyes are already glazing over from boredom, unfortunately, the short answer is: there are no simple answers.
Does Maternal Age Matter?
Most women who have had a baby or are trying to have one know about the dreaded “Advanced Maternal Age” label. It kicks in at 35 years old, when, truthfully, most of us feel pretty great and not old at all. In some ways science backs up our youthful feelings. While our *eggs* might be considered out to pasture past 35, the uterus still has a few good years left before heading over the hill. Transferring multiple embryos doesn’t actually increase your chance of IVF success until the age of 38 because generally a healthy uterus is in tip-top shape up until then. A more important consideration when weighing how many embryos to transfer in the case of a carrier who is 38 or older would be to look to the age of the woman who the eggs were collected from.
Fresh vs. Frozen?
This is an area where the knowledge base is evolving rapidly. It used to be that fresh transfers were the gold standard and had much higher success rates. As technology has evolved and vitrification (freezing) techniques have improved, the frozen transfer rates have steadily caught up. There are many theories for this, including the thought that a frozen transfer allows better control of the uterine environment before transfer, thus allowing doctors to wait to transfer until the environment is most receptive for implantation; as opposed to with fresh cycles where when the uterine time is right the embryos must be ready to go (or, vice-versa – if the embryos are ready, throw them in no matter what the uterus looks like and cross your fingers – and legs)! A frozen transfer, especially in the case of a woman where her own embryos are being re-implanted in her own body, also allows the body to recover and rest from the strain of egg stimulation and retrieval.
How about PGD?
Pre Genetic Diagnostics (PGD) is one of my favorite technological advances out there! I am definitely sensitive that some people do not like it and refuse to use it; and that is their choice. That said, a good number of times that an embryo fails to implant or a woman miscarries, it is most likely because there was something wrong with the embryo and the embryo was not going to survive no matter how favourable the uterine environment provided. PGD allows intended parents to move forward with only the embryos that actually have the best chance of surviving; there is a definite proven increase in success rates when it is used. IVF is expensive and can be heartbreaking enough; it makes sense to do everything in your power to increase the chances of success. [If you don’t want to feel responsible for things such as gender selection, you can ask the clinic to not disclose those things to you and select solely based on the embryo number and grading system!]
What if I Transfer Multiple Embryos?
This is the big question. Interestingly, the results are not always what you would logically think. A recent study published in the UK found that if two embryos of unequal quality were implanted (ie, one is good or very good and the other poor), there was actually a 27% *decrease* in the chance that implantation would occur. More isn’t always better. Sometimes more is just more. Additionally, if you do transfer multiple embryos and more than one implant you are looking at a tough decision between selective reduction and higher order multiples. Multiples carry much greater medical risk for the mother or gestational carrier and are far more likely to be born pre-term, which can leave them with a host of lifetime medical problems; or at the very least a very hefty hospital bill to start off with!
The decision as to how many embryos to implant can’t be decided by proxy over the internet. It takes careful consideration in consultation with your reproductive endocrinologist, research and a lot of deep thought as to your risk (and financial) tolerance. No matter what number of embryos you choose to implant, I’m sending sticky thoughts your way!