I took breastmilk from Tucson, AZ to Puerto Rico December '08. We left the house Saturday 6 am spent the night halfway (so kids wouldn't have a horribly long flight day) and arrived in Puerto Rico Sunday afternoon and got the milk into a freezer about 3 or 4 pm Tucson time.
You are restricted to 2kg (4.4 pounds) of dry ice. I had a box with a high quality, heavy duty styrofoam insert. The box measured 1 cubic foot. When I unloaded it there was just the final remnants of dry ice in the top of the cooler (in a little cardboard shelf.)
I was nervous the whole way. I carried the milk on board the plane and would not check it. If it was lost, I was in trouble. Most of the security people were not aware of dry ice regulations. A couple places insisted I open the box. One place I talked out of doing that so it would stay cold. On the way home we passed through Denver and they would not be convinced. I wrote on the side of the box "Keep Frozen. Human Milk for Baby."
So, it could probably be done depending on how long you will be traveling. The thing to check into is the laws in the country you're going to. One mom on another forum was told she could not adopt when the country found out she was going to nurse. (Although a year later they reversed that, she'd already been to the country once, lost on that child, and had to wait for another child.)
Unless you are getting a brand new newborn, I, personally, would not hassle with the milk. The baby is already on a formula it is used to. To suddenly change its diet, put it on a plane, and take it to a foreign world (your home) is a lot. The baby's already been on the formula. What's another week or two? You have so many other things to worry about that stressing over milk seems like it would make things much more difficult. If you want to hassle with milk, go for it. I just don't think I would unless it was an itty bitty baby and even then I don't know what I'd do internationally. (Said by a mom that tandem nursed my bioson and adaughter starting when she was 6 hours old.)
