I use Stronghold and apply once a month to my bitch. She is due her puppies next Wednesday and her Stronghold is due around the same time. Is it ok to continue with the Stronghold whilst she has the puppies?
It is safe during pregnancy & lactation, but personally I wouldn't use it for routine ectoparasite control & only use it if there were a problem with fleas / mange.
I wouldn't use any unneccessary chemicals on a nursing bitch, no matter how 'safe' they are proclaimed to be. I also agree with Smudgley, we never use any 'routine' parasite control. We have only had to de-flea our dogs on one occassion in the past ten years with the aid of chemicals.