This is a good opportunity to take a look at some of the diseases commonly transmitted from mother to puppy. That said, here we go. First we need some background information. Most disease transmission from pregnant bitch to unborn puppy occurs via the bloodstream, across the placenta. Appropriately enough, this is termed transplacental transmission.
Puppies can also become infected with disease-causing organisms during the birthing process.
In addition, some diseases can be transmitted to puppies after birth through the milk of the mother. This is called transmammary disease transmission. The most common example of a disease transmitted from mom to pup is roundworm infestation, or ascariasis. Many adult dogs harbor larval forms of this parasite encysted in their body tissues. Transmammary transmission of roundworm larvae occurs as well, particularly in the first few days of the puppy's life.