First and foremost, if you find yourself in this situation, separate the guinea pigs IMMEDIATELY! Separate them even if you think the female is already pregnant. Why? First, she may NOT be pregnant yet. Second, females have a two-horned uterus and while rare can get pregnant in the second uterus while carrying a litter in the other (the condition is called superfetation). Third, if she is very definitely pregnant, you probably don't know when she will deliver. The female goes into heat in a big way within an hour or two after delivering. There is a very high likelihood that she will conceive again if the male is present.
hope this helps
The gestation period for Guinea Pigs is 62 to 70 days. The greater the number of babies the mother is carrying, the shorter the pregnancy. Most pregnancy are non problematic. Guinea Pigs are more prone to heat related death in the latter stages of pregnancy. They have been known to abort the fetus's if an alarming incident occurs. If you must pick up a GP who is pregnant, be sure and securely support her hind quarters.
No changes are visible in appearance or behavior during the first four weeks. The last two to three weeks, the mother to be will become quite "plump." This is expected as the babies will comprise more than half of her body weight. You can see the movement of and feel the babies during the last two weeks. If you are positive that the Guinea Pig you are caring for is pregnant, you will want to feed her alfalfa hay instead of Timothy to give her a bit more protein and calcium. It has also been observed that fiber may contribute to preventing hair thinning, a common occurrence in late pregnancy, so the hay becomes very important. In addition, she will twice as much vitamin C to prevent toxemia.
Mothers rarely need any help unless they are older and this is their first pregnancy. The hip bones grow closer together with age, unless she gives birth. Any Guinea Pig over six months of age is at great risk if she becomes pregnant. If you have a GP whom you suspect to be pregnant, taking her to a Vet to determine the expected birth date and arranging for a cesarian will save her life. One clue as to the date of the up coming birth is that the babies will be seen moving three weeks prior to their emergence.
The birth process under normal circumstances usually takes place in the daytime and lasts for a maximum of 20 minutes. The first baby should appear after 5 minutes of labor. The time between the birth of each of the babies is between 3 and 5 minutes. Guinea Pigs will usually give birth to 2 to 3 babies. Sometimes only 1 will be born and on the rare occasion a Guinea Pig may have up to 8. If the labor extends longer, be prepared to rush her to the Vet. She could die of exhaustion. She will remain sitting while the babies emerge underneath, head first. She will pull the ambiotic sac with her teeth by reaching between her legs. As the babies appear she will clean them off as they appear. When all have been born, a bit of blood and the placenta will appear. She will eat the latter.
The Mother will not build a nest prior to the birth. You will want to separate her from any other GP's to avert any mishap and make sure she has a clean place to take care of her young. Give her some extra soft bedding, certainly not alfalfa hay which is quite scratchy. Care Fresh is very good bedding for young GP's.