Undernutrition among women of reproductive age is more common in South Asia than in any other region. In South Asia, the prevalence of maternal undernutrition varies between 10 and 40%. There is a scarcity of data on the contribution of small intestinal (SI) microbiota to pathogenesis of Environmental Enteric Dysfunction (EED) of malnutrition, as it is difficult to obtain gut biopsy specimens from malnourished individuals, especially children. The Bangladesh Environmental Enteric Dysfunction (BEED) study, involving participants who live in an urban slum (Mirpur) in Dhaka, provided an opportunity to examine the role of the duodenal microbiota in the pathogenesis of EED in children and also performed esophagogastroduodenoscopy (EGD) on thirty-eight 18-45-year-old malnourished (BMI\<18.5 kg/m2) women residing in the same resource-poor setting of Mirpur, Dhaka who failed to respond to an egg/milk/micronutrients- based nutritional intervention comparable to that given to children. In this intervention component, beginning at the end of the first trimester, low-BMI (\<18.5 kg/m2) pregnant women (aged 18-35 years) will be randomly assigned to receive either Microbiota-directed Balanced Energy Protein (MD-BEP) or Ready-to-Use-Supplementary Food Balanced Energy Protein (RUSF-BEP) for the duration of their pregnancy and during the first 3 postnatal months, in addition to standard antenatal care. A parallel cohort of age-matched normal-BMI pregnant women who will not receive any nutritional intervention will serve as a reference control group.