Gestation, birth, caring for newborn pups, and the one rule that stops a herd from exploding: separate the sexes.
Guinea pig babies, called pups, are astonishing: born fully furred, eyes open, and able to nibble hay within hours. If you keep a mixed group you will meet them sooner or later, so here is what to expect and how to keep numbers under control.
Gestation is long for such a small animal, about 59 to 72 days, and a pregnant sow can become huge. She needs extra vitamin C, plenty of hay, and calm handling. Most importantly, a sow can fall pregnant again within hours of giving birth, so the boar must come out well before the due date.
Litters are usually 2 to 4 pups. They arrive ready to go: they will nurse for about three weeks but are eating hay, pellets and veg within a day or two. Keep the nest quiet and let mum do her thing; step in only if a pup is cold, ignored, or not moving.
Boys can breed from around 3 weeks old and girls from about 4, so the pups must be sexed and split into a boy group and a girl group by three weeks, or you will have a second generation on the way. Our how to sex a guinea pig guide helps, and a rescue or vet can double-check.
Last updated August 2026 · Written from years of keeping long-haired guinea pigs in the Houston area. This is general care information, not veterinary advice. For anything medical, please see an exotic vet.
