Sudan fertility has been in decline according to data of 1983 census, 1993 census, 1999 SMS and 2008 census, declining from 6.1 in 1983 census to 5.6 in 2008 census, putting the country in the first stage of demographic transition.This study focuses on the possible causes of the declining fertility in the East of the Sudan. The overall objective of the study is to update our knowledge and information in the demographic realities in the east of Sudan. To achieve the objectives of the study a multi-choice questionnaire was developed to interview the study targeted population. In addition, a semi-structured interview was held with a group of obstetricians to assess the level of infertility nation-wide and role of the biological factors that may affect fertility. There is a correlation between proximate (direct) and indirect fertility determinants, showing a modest influence of the indirect on the proximate determinants. A more in-depth search of the roots of the declining fertility in the Eastern Region is highly recommended.