Abstract: This paper is an attempt to explore the current and future fertility trends in South Asian countries, 1980-2040s. The demographic impact of rapid declination in the general fertility pattern has been studies and obtained a significant change in the fertility rates in South Asian countries. The results of this studies also shows the fertility transitions has begun in South Asian countries, its impact varies from country to country. As the fertility and crude birth rates reduce the growth rate of South Asian countries are also reduce in parallel way. Afghanistan shows an extra ordinary nature in 1980s to 1990s.