Typically whenever Guinea pig breeders decide they want to start reproduction guinea pigs they do so with the idea that there will only be a couple children. The reality is that the average litter size can be from three to eight babies. Having more guinea pigs than one designed leads to a cascade of problems. First, all opposite-sex animals must be divided as baby males can actually impregnate the mom at 3 weeks of age. This means an extra crate (and maybe more) will be needed along with the present set up as the children are young and insecure.