Chakaria HDSS covers a population of 120,000 living in 21,000 households within the surveillance area. In first round, 4,903 children aged less than 3 years listed through household visit during July-September, 2011. All new pregnancies of 32,889 women are registered and followed-up until their pregnancy termination since July 2011 during quarterly . All live births are included in the child cohort of aged less than 3 years. A list generated from the database of children aged <3 years is used to record and update. The following exposure and outcome variables are collected using the form (Appendix B) .
