SART, in conjunction with, The American Society for Reproductive Medicine (ASRM), has published guidelines for the recommended number of embryos to transfer (add to link). These guidelines are based on SART-sponsored research which continually evaluates success rates around the country.  This helps to determine the optimal number of embryos to transfer, based on specific patient characteristics, like age and history of prior IVF.  Patients may require several cycles of treatment to have a baby. Success rates remain fairly constant over several cycles, but may vary greatly between individuals.  
In a bid to understand my chances of IVF success, I took a quick dive through the vast information available from these sources and came away thinking I had the information I needed. I skipped merrily along thinking things looked pretty promising after reading my chances of IVF working the first time was somewhere around the 40% mark. I naively thought that meant I had an 80% chance if I did two cycles, and that I’d definitely have a baby after three rounds at the most. Unfortunately as later reflection revealed, math and statistic just don’t work like this…
Repeated failed rounds of IVF can help identify causes of infertility. For example, if sperm and egg quality are normal, then the conception issue may be rooted at the embryonic or implantation level. In other words, if IVF fails to result in pregnancy despite successful fertilization, embryonic development or implantation may be to blame. Still this is a very expensive way to start getting answers.