Will tetra pak cartons leak during 11 hour flight on checked in luggage?

Our baby drinks prescribed formula milk that cannot be purchased in shops without a prescription. We will travel from the UK to Thailand for a few weeks and plan to bring supplies of milk with us. Some of it will be liquid packaged in tetra paks. I plan to put them in my suitcase but I wonder if they will leak. Does anyone know the likelihood of 200 ml tetra paks leaking in a checked in suitcase during an 11 hour flight? Also, I think that they should normally be kept at a cool temperature, but I wonder if the checked in luggage gets extremes of hot or cold? Thanks.