Guinea pig gestation depends on the size of the litter, with larger litters increasing guinea pig gestation time. The average guinea pig gestation period varies between 59 and 72 days, and litters number between one and six offspring, but as many as eight are possible. Some breeders predict guinea pig gestation by feeling for the number of young in the sow’s stomach. Movement might also help determine gestation because they begin kicking and moving about three weeks before delivery.
Most reputable guinea pig breeders recommend against breeding females until they weigh about one pound (453 g) and are between five and nine months old. If bred too young, the sow might be physically unfit to carry and deliver offspring. She also might lack the maturity to care for her offspring once they are born. Older sows, beyond nine months old, also should not be bred for the first time. After nine months of age, a female guinea pig’s hip bones might fuse, creating the need for a caesarean birth.
The actual birthing process takes between a half hour and an hour, depending upon the size of the litter. During the guinea pig gestation period, the sow does not make a nest or prepare for birth. The young are commonly born at dawn or dusk when guinea pigs are most active, but the sow usually does not give any sign that birth is imminent. She commonly delivers a baby guinea pig every five minutes or so.
Females break the sacs enclosing newborns with their teeth immediately after birth so they can breathe on their own. After the entire litter is delivered, the placenta is expelled and eaten by the sow before she cleans up any blood and waste and licks each new guinea pig. After most guinea pig deliveries, the sow gathers all the babies into a corner of the cage, where she puts them under her to keep them warm.
Males should be removed from the cage before the sow gives birth, because she typically comes into season again within an hour. Other pregnant sows should also be isolated when guinea pig gestation nears completion. When a sow begins the delivery process, it might cause other pregnant guinea pigs to deliver prematurely. Any unusual stress during guinea pig gestation might also cause abortion or premature birth of stillborn babies.
Cavies, or guinea pigs, are born with teeth, hair, and claws, and are able to eat solid food on their day of birth. They nurse about every two hours, taking turns at the sow’s two teats. After weaning, which generally occurs at three to four weeks, males should be sequestered from females because they become fertile and will mate with the sow or female cavies in the litter.