Background: South Asia has a large proportion of young people in the world and teenage pregnancy has emerged as one of the major public health problem among them. The objective of this study is to systematically review to identify the risk factors associated with teenage pregnancy in South Asian countries. Methods: We systematically searched MEDLINE, EMBASE and CINAHL database (1996 to April 2007) and web-based information. Inclusion criteria were the English-language papers available in the UK and describing teenage pregnancy in South Asia. Results: Out of the seven countries in South Asia, most of the studies were related to Nepal, Bangladesh, India and Sri Lanka. Socio-economic factors, low educational attainment, cultural and family structure were all consistently identified as risk factors for teenage pregnancy. Majority of teenage girls are reported with basic knowledge on sexual health however, very few of them have used the knowledge into practice. Both social and medical consequences of teenage pregnancies are reported consistently along the most of the studies. Utilization of health services, which is a protective factor, remains low and consistent. However, teenagers agreed to delay the indexed pregnancy if they would know its consequences. Conclusions: In South Asia, many risk factors are a part of socio-economic and cultural influences. This systematic review is limited by the amount and the quality of papers published on factors associated with teenage pregnancy. In particular, future research in South Asian countries is needed with standardised measures and methodologies to gain an insight into observed variations in pregnancy rates.