What To Do With Embryos?

Francesca Minerva (what a cool name) at Practical Ethics gets into the sticky morality of adopting embryos:

[I]f the main concern of couple who adopt embryos is to save as many embryos as possible because they consider them as morally valuable as already born children, why shouldn’t they adopt children who are already born?  In-vitro fertilization involves costs and health risks for women that adoption does not involve. It seems, then, that anything equal, adopting a child instead of an embryo is a more rational choice.

Moreover, if the goal is to save as many human lives as possible, we need a reason why an embryo is more entitled to be “saved” than a five year old child, for example.