For children in the poorest countries in the world, their chance of survival depends on the length of the period between their birth and the birth of the previous sibling, according to a new MPIDR study. In some cases, increasing the time between births by just one year can reduce the risk of infant mortality by about 50 percent.
source https://www.lifetechnology.com/blogs/life-technology-news-blog/in-poor-countries-birth-spacing-affects-infant-mortality