no vet is needed, seperat the male from the female as soon as possable because guinea pigs can breed again immedietly after birth, feed the mom alfelfa hay, but the male timothy hay. give the female extra pellets, and give her lots of dark green veggies. when the babys are born the mom will take care of things, just make sure the sides of the cage are high enugh that the babys cant stick there head through the bars(they can get stuck) if all you have is a small pet store cage, that will be fine for the nursing mom, for the male, by some organizer cubes, they come in grids, and a sheet of coroplast and build a C&C cage they are large, flexable, collapsable, and cheap. when the babys are 3 weeks old(or when the males start making Rumbling sounds and wiggling their butts) move them to the C&C cage with their dad. here is a website that tells you how to make a C&C cage. http://www.guineapigcages.com/ and here is a link to our guinea pigs site and you can check out our piggies, and there baby pics, and missy's page has pics of her pregnant.
http://users.accesscomm.ca/k9furkids/gp/index2.html