Background: Dimensions of social capital relevant to health in pregnancy are sparsely described in the literature.This study explores dimensions of social capital and the mechanisms in which they could affect the health of ruralSri Lankan pregnant women.Methods: An exploratory qualitative study of solicited diaries written by pregnant women on their social relationships,diary interviews and in-depth interviews with key informants was conducted. A framework approach for qualitativedata analysis was used.Results: Pregnant women (41), from eight different communities completed diaries and 38 post-diary interviews.Sixteen key informant interviews were conducted with public health midwives and senior community dwellers.We identified ten cognitive and five structural constructs of social capital relevant to health in pregnancy. Domesticand neighborhood cohesion were the most commonly expressed constructs. Social support was limited to supportfrom close family, friends and public health midwives. A high density of structural social capital was observed in themicro-communities. Membership in local community groups was not common. Four different pathways by whichsocial capital could influence health in pregnancy were identified. These include micro-level cognitive social capital bypromoting mental wellbeing; micro-level structural social capital by reducing minor ailments in pregnancy; micro-levelsocial support mechanisms promoting physical and mental wellbeing through psychosocial resources and healthsystems at each level providing focused maternal care.Conclusion: Current tools available may not contain the relevant constructs to capture the unique dimensionsof social capital in pregnancy. Social capital can influence health during pregnancy, mainly through improvedpsychosocial resources generated by social cohesion in micro-communities and by the embedded neighborhoodpublic health services.