When I had a miscarriage the doctor told me that about 20% or pregnancies ended in miscarriage due to a genetic abnormality. So the 40% thing does sound higher than the average for non IV pregnancies. But I'm not a doctor either.
Yeah, but I have heard there are many that simply never get to the implantation stage --- and hence, no knowledge of pregnancy, merely a normal period.
To me, it sounds like genetic material may unite, but God chooses not to breath life into it, for whatever reason He has.
(No Biblical basis for the above, just a hunch.)