when is the next heat?

Typically 6 months after delivery. Dogs don't always stick to an exact schedule...nature's funny that way. If you don't want her to go into heat, spay her. If you intend to breed her again, you should skip a heat cycle. Over-breeding can cause problems with the pups and the mother. A woman burns 500 calories every time she breast feeds...just think of what a dogs body goes through creating multiple babies and then feeding them for 3-4 weeks. She'll need lots of time to rest and recuperate before being bred again.

Usuall it is 6 months after delivery, at least that is how it has been with all the dogs I know. Sometimes it is a little longer though.

ITs usually after the last heat but some will go a bit longer after a litter.

its after the last heat