OBJECTIVE: To explore the factors affecting intra-household food allocation practices to inform the development of interventions to prevent low birth weight in rural plains of Nepal. DESIGN: Qualitative methodology using purposive sampling to explore the barriers and facilitating factors to improved maternal nutrition. SETTING: Rural Dhanusha District, Nepal. SUBJECTS: We purposively sampled twenty-five young daughters-in-law from marginalised groups living in extended families and conducted semi-structured interviews with them. We also conducted one focus group discussion with men and one with female community health volunteers who were mothers-in-law. RESULTS: Gender and age hierarchies were important in household decision making. The mother-in-law was responsible for ensuring that a meal was provided to productive household members. The youngest daughter-in-law usually cooked last and ate less than other family members, and showed respect for other family members by cooking only when permitted and deferring to others' choice of food. There were limited opportunities for these women to snack between main meals. Daughters-in-law' movement outside the household was restricted and therefore family members perceived that their nutritional need was less. Poverty affected food choice and families considered cost before nutritional value. CONCLUSIONS: It is important to work with the whole household, particularly mothers-in-law, to improve maternal nutrition. We present five barriers to behaviour change: poverty; lack of knowledge about cheap nutritional food, the value of snacking, and cheap nutritional food that does not require cooking; sharing food; lack of self-confidence; and deference to household guardians. We discuss how we have targeted our interventions to develop knowledge, discuss strategies to overcome barriers, engage mothers-in-law, and build the confidence and social support networks of pregnant women.