Guinea pigs are friendly pet rodents that originated from South America. Guinea pigs on a good diet usually have a life span of 5 to 6 years. Female guinea pigs (sows) are very prone to problems with their reproductive tract. It is very common for sows to have problems delivering pups (dystocia) and even more common for older sows to have ovarian cysts.
Dystocia is defined as an inability of the sow to deliver her litter normally. If female guinea pigs are to be used for breeding, they need to be bred for the first time when less than 6 months old. This is due to the changes in the pelvic canal. The sow’s pelvic canal has to expand in order to deliver the pups. The pelvic canal can expand from 1 to 1.5 inches during delivery. After 10 months of age in an unbred sow, the pubic symphysis will calcify and become permanently fused. This no longer allows her pelvic canal to expand and no longer allows her to deliver her pups.
Accidental litters can cause the same problems as planned litters. If you do not plan to breed your guinea pig but will house her in a pair or group, it’s critical not to expose unspayed female guinea pigs to unneutered males.
The gestation period in guinea pigs ranges from 59 to 72 days. The average gestation time is around 68 days. Sows typically have the pups quickly and deliver the entire litter in 30 minutes. If the sow starts to have contractions and cannot deliver a pup within 15 to 20 minutes, she is having a problem and medical treatment is necessary. In a young sow with an expanded pelvic canal, your veterinarian may be able to manually assist the sow with the delivery. In an older sow that is being bred for the first time, it is likely that the pelvic canal cannot expand enough to deliver the pups, and a C- section is needed.
Unfortunately guinea pigs in distress do not handle anesthesia and surgery well, so the prognosis is guarded to poor. Prevention of dystocia is much better than treating it. This can be done by breeding the sow at a young enough age (before 6 months of age) to insure the pelvic symphysis has not fused, and the pelvic canal can expand during delivery. Other options are to prevent interaction with an unneutered male guinea pig or to spay female guinea pigs when they are young, healthy and can tolerate the procedure better.
The other problem with the female reproductive tract is ovarian cysts. It has been reported that 66 to 75 percent of the sows between the ages of 3 months to 5 years have ovarian cysts. Sows aged 2 to 4 years of age are most commonly affected.
It is not known why guinea pigs are so prone to ovarian cysts. In most cases both ovaries are enlarged, but sometimes only one ovary is enlarged. A female guinea pig with an ovarian cyst typically has hair loss over the back and sides. Her abdomen enlarges and gives her a pear-shaped figure. Ovarian cysts are sometimes large enough to be seen on radiographs (X-rays), but are easier to see on an ultrasound exam.
Treatment of ovarian cysts is either by surgical or medical therapy. A spay surgery (ovariohysterectomy) is considered the best option. For sows with other medical conditions that would make surgery or anesthesia risky, medical treatment with hormone therapy can be tried.
It has not been commonly recommended to spay a female guinea pig, but considering how common problems of the female reproductive tract are, it may be time to change that. Young, healthy guinea pigs usually tolerate spay surgery just fine. Guinea pigs with dystocia or older sows with ovarian cysts do not do well with surgery. Always consult your veterinarian to determine what is best for your pet.