Pregnancy is very difficult for guinea pigs, with at least 20 percent on average of the mothers dying during birth. If you’re going to breed your sow, be certain she is young enough, because when they are older than around six months their hip bones grow too closely together to permit easy birthing. Think twice before you breed your guinea pig!
As soon as you suspect she has mated successfully, you should replace her usual timothy hay with alfalfa. Alfalfa has extra calcium and protein, both of which she very much needs. Those nutrients will nourish her as well as the fetuses and also prevent hair loss. She also needs extra vitamin C; you can give at least 10mg orally. Try giving her green peppers, more broccoli and kale.
A guinea pig’s pregnancy lasts about 9 or 10 weeks. While your sow might bear from one to six pups or even more, the average litter size is 3. If your sow is carrying more pups rather than less, her length of pregnancy will more likely be closer to 60 days than 70.
Weigh your guinea pig weekly to be certain she is gaining weight at a regular pace. By the time she reaches the seventh week of pregnancy, the babies will make up about half of her total body weight.
Once she passes the seventh week, you will be able to feel that the pelvic bones have spread apart. Once they are one to two finger-widths apart, it won’t be long until birth. Provide the guinea pig with a stress-free environment. If the male or other guinea pigs seem to get on her nerves, move them into another cage.
Your guinea pig is at risk of toxemia if the fetuses are taking up more energy than she can supply nutritionally. You should watch her carefully if she is too fat and moving very little or stops eating.
Most guinea pigs give birth in the daytime and it will take about five minutes to birth a pup. Each pup will have its own amniotic sac, and usually the mother removes it and eats it. If labor takes much longer than 20 minutes, she may require emergency medical attention. The pups will be fully furred and have their eyes open. They will want to eat solid food within a few hours of birth.
The mother remains at risk for some medical complications for a few days after giving birth, so keep a close eye on her. It takes two or three weeks to wean pups. You must be prepared to handle the litter of newborns, and remember that males can impregnate their mothers when they are only three weeks old.