Actually, one of the arguments against snowflakes, is that there's a concrete scientific REASON these embryos are the 'spares'- they were lesser quality/less likely to develop into an eventual sucessful pregnancy.

When a couple undergoes IVF, when the embryos initially came together, those most likely to develop into healthy pregnancies that can be maintained through to term are those used for initial attempts at implantation. Simply put, due to a number of reasons, not only scientific, also expense and the emotional hell that can be related to failed tries, those most likely to result in a viable pregnancy are skimmed off and used first.

Couples may go through a number of rounds of attempts before a successful pregnancy and birth occurr- if ever. If they wish to try for a second or third child etc out of that same initial batch of preserved embryos, the quantity, and quality diminishes further. Eventually they're left with frozen embryos, some that may be viable, many that may be less viable.

By the time the couple has finished with their attempts at successful offspring, the 'spares' from that process, if passed on to the transferance process are in turn less likely to gestate.

Which means, the embryo "adopters" may have to go through repeated attempts, and much emotional heartbreak along the way, with no guarentee of eventual success. To say nothing of the expenses related to each attempt at implantation.

What about incompatibilities between "mother" and embryo? One known problem with natural pregnancies is the Rhesus Factor and its effects on mother and foetus during pregnancy. I shudder to think what other incompatibilities there may be when the host mother has no genetic relationship with the embryo whatever. This may be one of the reasons why this lady became a serial killer (according to her own logic), murdering seven embryos along the way [/snark].

In fact, when I read this article, the first thought that went through my mind was: "The Boys From Brazil."