Labrador pregnant by her brother

Question
I Have a black labrador she is almost 3 years of age and I have her since she was about 8 weeks old. There is a dog from the same litter as she, that lives next door. She is always been an inside dog but during Christmas I went on vacation and she stay outside during that time when we came back from vacation about three weeks later she started ackting funy and her teets got big and now we know she is pregnant becouse we can feel the puppies inside her belly. My consern is that my neighbor told me that he has seen my dog with her brother a couple of times "mating" and I was told that the puppies can come out with birth defects. How true is that? I understand that they are from the same litter but not the same dad.
Please help me understand what are the consecuenses so I can deal whith the problem.
Madeline Aponte  

Answer
Hi Madeline,

It is possible for the dog next door and your female to have different sires. A female is covered with two different males to ensure pups. Not very ethical but doable. DNA testing will eliminate any doubt about parentage.

Interbreeding should only be done on "the best of the best" and experienced breeders will use it to hone in on a specific trait.  Inbred dogs will produce "type" good and bad. This litter must be carefully evaluated as you will get extreme on both ends of the good and bad scale. A reputable and experienced breeder will "cull" the litter (have the pups all fixed).

It may be advisable to have your female fixed after this litter so accidental breeding can't take place.

Good luck.