You can look at the graph here
This graph compares the Infant Mortality Rate and the Income per person of many countries. This graph shows a trend displaying how income per person affects the infant mortality rate. When the income per person increases, the infant mortality rate decreases. Sub Saharan-Africa tends to be around the same zone in infant mortality rate varying a little in the GDP per capita. The causes to this might be not a very good healthcare and wars that are occurring within countries or against other countries like the genocide occurring in Sudan. Another cause might be diseases like HIV and Malaria. Through the years the infant mortality rate has been decreasing and the GDP per capita is increasing. Sub-Saharan Africa is the only region that does not vary very much. The GDP increases slightly but the infant mortality stays the same. Sub Saharan-Africa is the region with the lowest Infant Mortality Rate and income per person.
Humans have advanced in healthcare, this is why the infant mortality rate has reduced a lot (over 200 children less die out of 1000). New technology and the advance in medicine has helped children survive. Most of the population in Sub-Saharan Africa does not have access to healthcare this is why many children die at birth or under the age of 5.
I expected to see a graph similar to this but I wonder why Sub-Saharan Africa does not advance as much as the other countries. This similar thing happened in other graphs with this region. The more money a person has the more access to healthcare they have and to medicine. They have more money to take care of their children and feeding them correctly. The countries that have a higher infant mortality rate might be because they have less access to medicine and to supplies to take care of the mother and the child.