It does not really matter whether the father is present or not at the birth. Usually, he won't really care about it, and will stay away. But in some cases the father may choose to be helpful and clean the newborns. Don't be alarmed when blood comes out of the mother after all of the babies have been born. That's a natural part of the pregnancy.

When will I be able to tell that the female guinea pig is pregnant? After about four to five weeks after the mating, the female will become more plump and round around the belly area. She will definitely be heavier. If you put the pregnant female on your lap, you can usually feel the babies moving around inside her.

When can I handle the babies? You are allowed to handle the babies as soon as they are born.

When can the babies be separated from the mother? Baby guinea pigs cannot be separated from their mothers until 3-6 weeks after they are born. This is because the mother needs to wean them and continue feeding them with her milk. Intersting enough, baby guinea pigs can start to eat hay and dry food soon after they are born.

Also, baby guinea pigs are born with their eyes open, and already have their coat of fur. They can run around and play with the other young as well, although they do stay close the mother a majority of the time.

When will the babies be able to mate? The females will be able to have babies when they are about 6 weeks old. Males will be able to mate when they are about 10 weeks old. So make sure that they are separated a good time before those times because a brother guinea pig can mate with his sister! Inbreeding in a family like that is not a good idea, as it can cause genetic defects in later generations.

Should I separate the other guinea pigs from the pregnant one while she is giving birth (and after it)? It varies for different guinea pigs. Some guinea pig mothers would prefer to have her space while giving birth, while others want to have a mate around. This is the same case for having the father present during the birth of the babies. I would go the route of separating the mother from any other guinea pigs while she is giving birth and for at the very least, a couple of days after the birth.

How do I tell what sex the babies are? It is not always easy to tell what sex a guinea pig is. When I first got my male guinea pig, Chestnut, I had to double-check that he was actually male, as the people at the pet store said he was. Sometimes the people at pet stores will accidentally misinform you about what the sex of your animal is. I know this from experience because we got some hamsters and a couple weeks later we had babies to take care of when we thought that originally both hamsters were male.
     But what you need to do is set them on your lap facing you. Then turn them vertical so that you can easily see their stomach. To figure out what sex a guinea pig is, all you have to do is gently push on the stomach down near the guinea pig's private parts. You can do this with just two fingers, usually with your index (pointer) and the middle finger, and do this very gently. If the guinea pig is a male, a penis will emerge in the private area. If it is a female, nothing will happen. Also, in a male, there is a greater distance between the penis and the anus. In the female, the private part and the anus are closer together.