Since 1990, maternal deaths have decreased by 45%. This information is given by the World Health Organization in a document that explores the reasons for mortality during pregnancy or in childbirth. According to the WHO, most of the causes can be prevented through increased investment in the care for pregnant women. In 1990, more than half a million women died during pregnancy or in childbirth, while in 2013 the phenomenon struck 289,000 women. The figures are still too high, with 33 maternal deaths worldwide per hour. Moreover, there is still a very evident difference between rich and poor countries. In sub-Saharan Africa, for example, the risk that a 15-year-old girl will die during pregnancy or childbirth is one in forty. In Europe, the risk is only one in 3,300. While, on the one hand, it is necessary to increase investment in health care in the poorest countries, on the other, maternal mortality is also increasing in some rich countries, like the United States. According to experts, more than one fourth of the maternal deaths are due to complications during pregnancy, caused by pre-existing conditions such as diabetes, HIV, malaria and obesity.