In underdeveloped nations, women usually enjoy a low economic and social status. This means that women generally receive little or no education, and do not participate in the workforce. This reduces the opportunities for economic advancement for women, and makes them dependent on men for subsistence. This situation leads to early marriage, as well to a long reproductive life. In turn, this leads to a high fertility rate.
I'd think because when woman are used mainly for babies and household chores, they will be less obligated to other factors(work, studying, etc), which usually restrict their abilities to have kids.
