You may have no idea that your fluffy princess is expecting until weeks after conception. But after several weeks, you’ll start seeing changes in her nipples.
Right around 40 days after conception, your little friend’s nipples will start swelling. They’ll get bigger as the mammary glands start producing milk -- she could even start leaking milk. In some cases, the nipples may even get darker in color. Her nipples could stay swollen throughout the duration of her pregnancy, while she’s nursing and possibly long after her pups leave the nest, if she nursed for a long period of time.
Female dogs in heat also go through nipple swelling during or after heat cycles. Just because her nipples seem engorged, doesn’t necessarily mean she’s pregnant. Only your vet can determine if she’s actually carrying pups. Lastly, it is possible for your dog’s mammary glands to become infected if she is indeed pregnant and lactating. If the swelling leads to pain, she refuses to eat or you see pus coming out of her nipples, it’s time to get her to the vet right away.