So here is the nuance to this issue. There are viable embryos and there are non-viable embryos.
In basic terms nothing really matters till day 5. Day 1 they tell you how many eggs they got and many fertilizer, then Day 3 update on how many are growing. Day 5 is how many are an embryo. At this point they do genetic testing and freezing. Almost all IVF places prefer or almost exclusive doing Frozen so they can genetically test.
Genetically testing is essentially telling you whether the embryo is viable or not. If it doesn't have enough chromosomes it is not viable and will result in failed transfer or a miscarriage. Now if you have non-viable embryos you can either keep them frozen at a couple hundred dollars a year, or discard them, or donate them to science. Most embryos are 50/50 viable to non-viable. I hope we agree on the term Non-viable. The testing does provide some information regarding genetic diseases as well but you will know that mostly beforehand due to blood work. But essentially this is why IVF has to be able to discard embryos there is no way to guarantee you will get a viable one.
The doctors I talked to will not transfer more than 1 viable embryos at a time. The information is a bit dated with transferring 2 or more, as that was done with fresh transfers in older woman due to egg quality. Given the pain and suffering most go through to get the pregnancy stage, I cant imagine abortions being performed. I will caveat this, with I am sure it happens, people can be horrible.
I would also point out most IVFs are done because of a medical reason. Such as reoccurring miscarriages or ectopic pregrancies. To get to a egg retrieval a woman has to give herself anywhere between 30 and 60 shots in the stomach. Then the retrieval and then another 30 to 60 shots for transfer. Then you pray.
I have heard people say you should have to implant the non-viable embryos, which is the equivalent of wishing someone to have a miscarriage.
I have also had people say that it is up to God if you get pregnant and should have a baby. Which to means I guess we shouldn't see doctors for medical answers.
The only personal thing I will add is that we still have our non-viable embryos, I am not ready to let them go.
I dont want to this to be a case of what-aboutism. John/Kate plus8 didn't follow medical procedures and had sex after she got her final shot. I'm guessing octomom did something similar. But to point out a few bad actors (think poaching, gun murders, etc) amongst an otherwise ethical practice is a flawed argument.
And to answer the question no one asked, but life ends when the heart stops. Life starts at the heartbeat.
Anyways not sure if they helps or not, but at least it is another data point.