There are various signs that indicate a pregnant Chinchilla:

Increased Weight – Pregnant females will begin to put on weight at a pretty rapid pace, especially at the end of the pregnancy. This is why its important to monitor the weight of any females in a breeding program.

Increased Appetite – Females will begin to consume more food at this time, so always make sure fresh water, hay, and high quality pellets are available.

Behavior Change – Many females will experience a change in behavior from become irritated, fighting with the male or cage mates. Sometimes females who didn't like to be cuddled or held may want to become lap chins.

Lying on Side – lots of females will begin to lie on their sides, and often times near the end of the pregnancy you can actually see the babies moving in the moms stomach. Keep in mind that many chinchillas will sleep on their sides when they feel comfortable in their environment.

Feeling for babies – You should never palpitate moms stomach or squeeze hard while she might be pregnant, this could result in stillborns or lost of pregnancies. But if you can get a pregnant chin to stand in your hand or gently place your hand just barely against her stomach you can often feel babies moving.

Elongated Nipples – Between a week and the litter day a pregnant chinchillas nipples will extend to about the length of the fur. Right behind her armpits is usually the easiest place to spot the nipples.