What age do YOU think is good to spay a puppy?

I recently rescued a puppy from a private dog rescue. By law, upon adopting her I had to sign a contract saying I would spay her by 4 months of age. Doesn't this seem way too early? I know the reason they say 4 months is to avoid having the dog go into heat at around 5-7months, and getting pregnant their first heat, but still, couldn't the dogs have problems down the road because certian hormones produced by the ovaries affect development? It just seems so young.I didn't say I wasn't going to get her spayed when I said I would! I know I signed the contract, I was just asking for other people's opinions! Sheesh! Some people are so hostile...And I did talk to my vet. He won't even do it before 6 months, so I have to find a different vet.

before first heat cycle or 6 months of age

before their first heat and after they weigh at least 5 pounds.add- spaying BEFORE the first heat drastically reduces their risk of mammary cancer.