How old do female guinea pigs have to be to get them pregnant?

Male guinea-pigs can start mating when they are as young as 3 weeks old, although it is recommended that you make sure they been bred by six months old to make them a breeder.

Female guinea pigs can start having babies when they are three months old, however, it is highly recommended that you don't mate them when they are over a year old, due to pelvis bone fusion. A female guinea pig any older than a year old will have a dead litter before she will be able to produce a live litter.