This is the baseline report for the cost-effectiveness analysis of the Healthy Pregnancy Healthy Baby text messaging service, Tanzania (also more widely known as Wazazi Nipendeni), a Value Added Service (VAS) supported by the GSM Association (GSMA) as a part of the mNutrition programme. mNutrition is a global initiative supported by DFID, organised by GSMA, and implemented by in-country mobile network operators (MNOs) to use mobile technology to improve the health and nutritional status of children and adults in low-income countries around the world. This report forms part of the evaluation of mobile based services, which draws on a number of methods and interlinked components to gather evidence about the impact of the intervention in Tanzania supported by the mNutrition programme.