The nesting instinct manifests itself in different ways for every pregnant woman, but the majority will notice this at some point during their third trimester. Some of the more frequent urges that expectant mothers report include repainting the walls in their homes, cleaning and reorganizing their kitchens, and cooking large amounts of meals for freezing. It is also common to want to run your baby's outfits and bedding through the washing machine and to want to iron them. Some women get the urge to wash their pre-pregnancy clothes and put them back in the wardrobe too. Then, there are mothers who feel they need to go and get cards for their baby's birth announcements.
It is important to differentiate the preparations you make for your baby because you rationally know they are needed from the deep, immediate urge to organize and clean. We all experience the first, because baby's do need preparations. The second category is less rational when you want to scrub every corner of your bathroom over and over again, you bet that it is a bad case of the nesting instinct! Unless you want to do things that are physically irresponsible (like standing on high ladders to scrub the ceiling), go with your instincts and clean away. Know that your baby will be with you sometime soon! Also see, In your third trimester and bored? At-home entertainment ideas for women about to give birth.