Alas, there are not many stores that realize that except for this very special store. Adorably called Breastmates. http://www.breastmates.co.nz/ Not only does this store stock maternity clothes but it also features great deals on maternity underwear, breast pumps, nursing covers for those who wish to breastfeed their babies but don't want to bear their breast in public, nappy bags, and maternity pants.
Their selections range from cheap to reasonable price. They ship internationally and accept all types of major credit cards.
The website also features accessories, books on parenting, DVDs, and other things for the baby. There is also a section with advice and tips for young mothers.