It is normal for pregnant dogs to have some clear jellylike vaginal discharge early throughout the pregnancy. First the discharge is to help form a mucus plug to protect the puppies, but then it comes out before labour.
A transparent, odour-free discharge means that the dog is pregnant and forming a mucus plug. This is one way to diagnose pregnancy in a dog as soon as two weeks after breeding, according to PetEducation.com.
One week or less before labour begins, the mucus plug will come out of the dog's vagina in order to widen the cervix. This may look like a long ball of ear wax or like long strings of mucus streaked with blood, according to Dog Breed Info Center.
While in labour, yellow discharge comes before the puppy because the membranes around the puppy burst open. Sometimes a green fluid will come out as well, which is filled with the puppy's stools while in the placenta, but normally green discharges comes out after the puppy.
If it's been three to five weeks after breeding and there's a foul smelling, pus-filled or very bloody vaginal discharge, she could have a potentially lethal infection of her uterus called draining pyometra, according to "The Veterinarians' Guide to Your Dog's Symptoms."
All throughout the dog's pregnancy, some light pink discharge is normal but may be mistaken for pyometra or abortion, according to Hilltop Animal Hospital. When in doubt, check with a vet.