First: So sorry for your multiple loss. It is not easy as I have been there and it is very frustrating to get so close and it not work out. They should have told you the results of your D&C about a week after it happened. Did you start your next cycle immediately?
You can have your embryos genetically tested before you put them in but it is not a “standard” practice, and they charge you more for it, naturally. They usually only recommend it for people who have chromosomal abnormalities in their families or with previous children. My understanding is they need to test the embryos on day 3 and then you need to freeze them all as it can take a week to get the results and then you can implant them in a frozen cycle once you find out which ones were normal.
Do you know what abnormalities were identified? Were you and your wife Karyotyped after the first miscarriage? They can test your chromosomes to make sure you are ‘Normal’ so you don’t mix wrong. That is your first step.
I had a miscarriage at 12.5 weeks and they did a D&C and they found it was Turner’s Syndrome which is one of the most common naturally found abnormalities that cause miscarriages. (I don’t think they even test for it when they do genetic screening) Since it wasn’t a genetic issue (like downs or trisomy 18) there was nothing more to do. Just a case of bad luck.
I would ask if your RE if they tested you and your wifes chromosomes. And ask about the genetic testing. Not sure you can do it now but it is worth asking what to do now about your mulitple losses.