[header] How to bathe a pregnant guinea pig [title] Select a shampoo. [step] There are all types of shampoos for pets. For your guinea pig, make sure the shampoo is made specifically for small animals (it should say so on the bottle). 
A small animal-specific shampoo will keep your guinea pig's skin from drying out or becoming irritated. Since your guinea pig is pregnant, the shampoo should also be non-medicated to prevent ingredients absorbing through her skin that could harm her unborn babies.