The first sign of a guinea pig pregnancy is an enlarged abdominal area. The stomach does not enlarge until later in the pregnancy, so often the pregnancy isn't noticed until halfway through the gestation period
The enlargement of the abdomen gives the guinea pig a narrow upper half and wide bottom half. Guinea pigs do not build nests, but a pregnant guinea may drink more frequently and move less the closer she gets to delivery. A separation of the pelvic region near the outside genitalia will develop about a week before she gives birth. Labor and delivery takes around 30 minutes, and litters can range from one to six babies.