Just popping into your thread. I don’t know the reason why the odds of success are pretty much the same with one embryo transfer or two, but reputable population-based stats certainly support that being the case.
The most recent report from the Australian Institute of Health and Welfare on Assisted Reproductive Technology in Australia and New Zealand states (at p vi):
“A continuing trend in ART treatment in Australia and New Zealand has been the reduction in the rate of multiple birth deliveries, with a decrease from 12% in 2006 to 7.9% in 2010. This was achieved by clinicians and patients shifting to single embryo transfer, the proportion of which increased from 56.9% in 2006 to almost 70% in 2009 and 2010. Importantly, this decrease in the multiple delivery rate was achieved while clinical pregnancy rates remained stable at about 23% per cycle”
The full report is available at http://www.aihw.gov.au/WorkArea/Down...id=10737423255 if anyone is interested.