Shedding light on maternal sunlight exposure during pregnancy and considerations for public health policy

Sunlight exposure during pregnancy could be implicated in the physiological development and growth of the fetus, as well as long-term health after birth. Although several studies suggest the involvement of ultraviolet radiation-mediated vitamin D synthesis, current knowledge regarding the effects of sunlight exposure during pregnancy remains limited. We aimed to (i) summarize the existing body of research studying the influence of sunlight exposure on fetal growth-related birth outcomes and long-term health outcomes and (ii) determine its implications for therapeutics and public health policy. Of the studies identified on birth outcomes, the majority (5/8) demonstrated an association between sunlight exposure and reduced adverse birth outcomes (e.g., low birth weight, preterm births, small for gestational age, etc.), 2/8 studies showed no association, and 1/8 suggested a negative association between sunlight exposure and reduction of these adverse birth outcomes. Of the studies examining long-term health outcomes, sunlight exposure during pregnancy was shown to promote skeletal growth and development (2/6), and reduce the incidence of multiple sclerosis (2/6), asthma (2/6) and pneumonia (1/6). However, several of these studies used different methodologies and populations making it difficult to compare and integrate findings. Based on these results, we examined: the importance of exposure at different stages of pregnancy, proposed mechanisms by which sunlight exposure could lead to optimal outcomes, epidemiological differences influencing the findings, and necessary practical considerations prior to the implementation of public health policy recommendations. While these findings are promising, more rigorous research is warranted to support these recommendations.