A premature baby boy lies in an incubator at maternity hospital in Karachi
A premature baby boy lies in an incubator in the natal intensive care unit at an Imam maternity hospital in Karachi October 28, 2011. The world's population will reach seven billion on October 31, according to projections by the United Nations, which says this global milestone presents both an opportunity and a challenge for the planet. REUTERS/Insiya Syed (PAKISTAN - Tags: POLITICS HEALTH)