We're still quite a ways for using this process for anything much bigger than a mouse - right now the nutrients are being supplied entirely via diffusion, without a working blood supply:

> At Day 11 of development — more than halfway through a mouse pregnancy — Dr. Hanna and his colleagues examined the embryos, only the size of apple seeds, and compared them to those developing in the uteruses of living mice. The lab embryos were identical, the scientists found.

> By that time, though, the lab-grown embryos had become too large to survive without a blood supply. They had a placenta and a yolk sack, but the nutrient solution that fed them through diffusion was no longer sufficient.

> Getting past that hurdle is the next goal, Dr. Hanna said in an interview. He is considering using an enriched nutrient solution or an artificial blood supply that connects to the embryos’ placentas.