Birth control in Islam

NPR did a great story about what happening in Pakistan (see link bellow). According to NPR, Pakistan is adding 4 million new persons to planet every year. It would be fine in a country that can provide for its people, but we simply cannot. So, I’m wondering what does Islam says about family planning b/c some molvi hazrats are issuing fatwas against family planning.

http://www.npr.org/2011/08/10/139382653/in-pakistan-birth-control-and-religion-clash?ps=cprs