If the birth rate is high, for example in some African countries, this indicates that women have more children due to higher mortality rates of children. Basically, women in poorer countries with a low quality of life have more children because the chances of some of her children dying young is high. They also want to make sure that at least a few of their children make it to adulthood. Whereas, in wealthier countries with higher qualities of life e.g. the US and the UK, women tend to have 2-3 children as healthcare is good and their children will almost always survive until adulthood.
