Can I safely worm my bitch, she is 4 weeks pregnant?

Our customer asked:
Can I safely worm my bitch, she is 4 weeks pregnant?

Our reply:
It is generally a good idea to avoid any medication in the first third of any pregnancy (3 weeks for a bitch). After that, most wormers are safe. Panacur or Drontal should be fine to use, though do not overdose. It is still important to worm the puppies several times while they are growing up. (A worm dose kills adult worms in the gut. Puppies get worms from microscopic larvae that travel to the pups in the uterus and through the milk, having never been in the gut of the mother. They are usually not killed by worming the bitch, unless you worm repeatedly. It is possible to worm a bitch every day for the last third of her pregnancy using Panacur to prevent this. Not many people consider this necessary. Otherwise you can start worming puppies from 2 weeks of age and repeat every 2 weeks until 12 weeks of age.)