This dataset was used to analyse the Low Birth Weight South Asia Trial (LBWSAT) cluster-randomised controlled trial. The trial generated data on maternal and child anthropometry, diet in pregnancy and early life, details of pregnancy, delivery and the first 1-2 years of life. All women of reproductive age (10-49 years) resident in the study areas were invited to participate in monthly monitoring of whether they have had or missed their period. We interviewed (and at certain times weighed or measured) consenting women with a positive pregnancy test at the following times: an enrolment (usually 8-20 weeks gestation), in early pregnancy (8-31 weeks), late pregnancy (32 weeks to birth), at delivery (within 72 hours of birth where possible) and at 4-6 weeks after birth. This means that different variables in the dataset came from different data collection instruments, which had differing capture rates. We failed to capture as many birth weights within 72 hours as planned due to conflict in the data collection team. This (non-blinded) cluster randomised controlled trial assessed the impact on birth weight and weight-for-age Z-score in children aged 0–16 months of a nutrition Participatory Learning and Action behaviour change strategy (PLA) for pregnant women through women’s groups, with or without unconditional transfers of food or cash to pregnant women in two districts of southern Nepal. PLA comprised a series of open women’s group meetings which pregnant women were encouraged to attend. A Female Community Health Volunteer facilitated each group, supported by a nutrition mobiliser. The groups (n=539) identified and prioritised problems associated with improving women’s intake of nutritious food in pregnancy, low birth weight and hand hygiene and implemented strategies for addressing these.

Participants were (mostly Maithili-speaking) pregnant women identified from 8 weeks’ gestation onwards, and their infants. Face to face interviews were held with women and their 'guardians' (often mothers-in-law) at their home for all interactions except the cross-sectional endpoint survey which was conducted at a central data collection point in the community. After pregnancy verification, mothers could be followed up in early and late pregnancy, after delivery (ideally within 72 h but this occurred up to 42 days), after 42 days and (cross-sectionally) within 22 months of birth. All quantitative data collection was undertaken using Comm Care or ODK data collection platforms installed on Samsung galaxy Y mobile phones. The mobile phone questionnaires had build in jump sequences and range restrictions for quantitative answers such as dates, anthropometric readings and so on to limit implausible/ erroneous data entry. All women were identified with a QR-coded woman ID which had 3 digits appended to represent the pregnancy (in which LMP was coded). The QR code was scanned at the start of every interview to enable easy merging of cases by unique identifier. Anthropometric readings were taken in duplicate (with a third reading if duplicates differed widely) using standard Tanita BD590 weighing scales for infant / child weights, Tanita solar weighing scales for adult weights, Seca measuring tapes and "Shorr" height / length boards for height or length.