Dystocia in Female Guinea Pigs

Pregnancy is dangerous is all mammals, but can be lethal in female guinea pigs or sows because of dystocia. A sow's hip bones fuse together when she is about seven or eight months old. Guinea pig gestation is from 59 to 73 days. If a sow is going to be bred, she needs to be bred by the time she is six months old, otherwise the fetuses will be far too large to fit through her birth canal.

Guinea Pig Evolution

Domestic guinea pigs or cavies (Cavia porcellus) are thought to descend from wild cavy species in South American such as Cavia fulgia, but the exact species is unknown. Domestic cavies were first kept and bred by the Incas about 5000 years ago.

Although 5000 years seems a long time, it is barely a blip in the evolutionary time scale. Wild cavy females go into their first heat as early as four weeks old and are usually impregnated by the time they are six months old. Unless there weren't any males in the area, wild cavy sows probably never experienced dystocia.

But today's pet cavy is not kept in small herds but is usually kept separate from males or boars. Many sows do not have the opportunity to mate until long after their birth canals have been significantly narrowed. But by the time she is about seven months old, a change has come to her symphysis or a band of cartilage connecting the pelvic bones. This tissue toughens up. Because of toughening up, the pelvic bones loose their ability to relax and open up to the point where a fetus can slip through.

Accidents Happen

Guinea pigs will be guinea pigs and sometimes a sow may be accidentally bred, especially if she is from a pet store or has been suddenly abandoned at an animal shelter. In these cases, the pregnant sow needs surgery. If the pups are unwanted, then they may be aborted right away and the sow given a spaying. But if the owner wants the pups, then the veterinarian will wait to perform a Caesarian section. Unfortunately, the survival rate for a sow with dystocia is poor. If she does survive, she may not recognize her pups and refuse them.

Sources:

"The Guinea Pig Handbook." Sharon L. Vanderlip, DVM. Barron's; 2003.

Guinea Lynx. "Reproduction and Breeding." http://www.guinealynx.info/reproduction.html

Pet Place, "Guinea Pig Dystocia and Pregnancy Toxemia." http://www.petplace.com/small-mammals/guinea-pig-dystocia-and-pregnancy-toxemia/page1.aspx