Well it is now day 29 since the first breeding, still no physical signs Riva is pregnant but its still a little to early for that. I have read that you will really start to see outward signs about 5-6 weeks. If she is pregnant things inside the uterus are developing pretty rapidly now. I came across this info that explains pretty well:
By Day 30, the fetal puppy cells become committed to forming mucous membranes, digestive and respiratory glands, muscles, bone, the puppy’s circulatory, genital and urinary systems, the skin and hair, the nervous system and all of the puppy’s sensory organs–including the eyes, inner ear and peripheral nerves. During weeks four to six of pregnancy, the puppy’s organs, bones, eyes and spinal cord begin to fully develop. The fetus starts to actually look like a dog, with whisker buds showing on its developing face, and claws and toes differentiating on the feet. By week six, the fetal puppy forms skin pigments and your vet should be able to palpate the puppy and hear a heartbeat with a stethoscope, says the Doberman Pinscher Club of America website.
This picture also shows how the puppies are placed in the uterine horns.
How God has designed all creatures for reproducing their species is absolutely amazing!