Outcomes at birth such as prematurity and birthweight are important determinants of later life health and social outcomes including education attainment, cognitive and behavioural development and a large number of health outcomes. Recently, it has become clear that characteristics of the physical environment, including air pollution, plays an important role in mediating outcomes of pregnancy. Vitamin D deficiency from lack of sunlight has also shown associations with pregnancy outcomes but this has not been replicated in intervention studies of vitamin D supplementation. Recent clinical evidence has pointed to a sunlight pathway that is independent of vitamin D, which instead mediates blood pressure through the production of Nitric Oxides in the skin from exposure to the UVA component of sunlight. This pathway might explain the lack of association with vitamin D supplementation and provides a plausible pathway for direct effects of sunlight exposure for pregnancy outcomes. In this study, we examined the effect of exposure to sunlight during pregnancy hypothesising that higher levels of exposure might reduce risks of premature birth and low birthweight.