Peter Anto Johnson is currently a graduate student in the Department of Paediatrics at the University of Alberta. His research interests place an emphasis on child & maternal health, public health, and risk prevention. He is the president and founder of the Canadian Coalition of Global Health Research Alberta Student Chapter, along with the creator of the Edmonton-based Physical Literacy for Active Youth (PLAY), a physical literacy program for children to promote long-term healthy habits and foster physical activity encouraging preventative health amidst our sedentary society. Peter is also involved in numerous social advocacy and research initiatives within his community and on a provincial-level. In 2018, his efforts locally earned him the City of Edmonton’s Mayor’s Award in the Youth category. Later in 2019, his accomplishments culminated in his distinction as Top 30 Under 30 by the Alberta Council of Global Cooperation.

“In my early childhood, I first recognized the significance of social and environmental determinants of health growing up in rural India. As a survivor of a near-death experience in my infancy, I became more aware of diseases and conditions affecting children that are a result of their environment. While I am incredibly fortunate to have survived, many children do not survive or end up with long-term health outcomes due to environmental risk factors that cause diseases, which are often preventable. As a result, my graduate work has extensively focused on studying newborn health and preventing adverse health outcomes, for infants and children, which are preventable. Lack of sunlight in Canada may be a risk factor for adverse health outcomes in approximately 400,000 infants born every year. As a result, I was motivated to gain insight into current understandings on this issue, while determining effective strategies for prevention through this project.”

Sunlight consists of infrared, visible, and ultraviolet (UV) radiation and plays a critical role in regulating normal physiological functions including vitamin D production and synthesis of hormones such as serotonin in the brain [1], [2]; however little is understood about its effects during pregnancy on offspring. Exposure to environmental insults during critical periods of growth and development of the offspring could have severe consequences on its short- and long-term health [3], suggesting differences in exposure to sunlight during pregnancy could considerably impact immediate and long-term outcomes. This is highly relevant in both developing regions with an abundance in sunlight exposure, as well as in regions, such as Canada, where seasonal differences result in a lower amount of exposure to sunlight for several months of the year.

Overexposure to UV rays during pregnancy is associated with increased adverse risks in mothers including skin damage and cancers [4]. At the same time, exposure to UV, is essential for chemical reactions involved in conversion pathways of cholesterol to vitamin D for several functional roles, such as calcium and phosphate homeostasis, insulin metabolism, bone growth, and remodeling, cell growth mediation, and promotion of immune function [2]. Pregnant women are increasingly more susceptible to vitamin D deficiency [5], suggesting there is a greater demand for vitamin D in the body during pregnancy. Vitamin D deficiency during pregnancy is associated with outcomes including low gestational birth weight (BW), stillbirths, preterm birth, vitamin D deficiency, hypocalcemia, and childhood obesity [6]–[9]. Low BW (<2500 g), stillbirth, and preterm births are birth outcomes indicative of fetal growth restrictions, while vitamin D deficiency, hypocalcemia, and chronic health outcomes suggest long-term consequences of this deficiency in later development. These outcomes suggest a threshold amount of UV exposure may be critical for healthy offspring development.

Although no international or national guidelines exist about the amount of UV or sunlight exposure pregnant women should have, the World Health Organization’s INTERSUN Programme developed in 1992 remains one of the first international standards to include UV exposure as a health consideration [10]. However, it is limited and only provides general recommendations to the public to prevent adverse health risks of UV exposure. Clinical trials suggest vitamin D supplementation is ineffective in reducing long-term risks in offspring associated with maternal vitamin D deficiency [11]. Moreover, using supplementation could have availability, cost-effectiveness, and ethical (vegetarian or vegan diets) issues. As production of vitamin D depends primarily on exposure to sunlight [12], there might be therapeutic value in considering effects of UV exposure during pregnancy on offspring outcomes.

In a recent review, it was determined the majority of studies showed an association between sunlight exposure during pregnancy and positive immediate and chronic offspring health outcomes including higher BW, less preterm births, less small for gestational age infants, enhanced skeletal growth and development, reduced incidence of diseases including multiple sclerosis, asthma, and pneumonia later in life [9]. Ultimately, these results and those in current literature suggest the need for policymakers, healthcare professional, and related stakeholders to take action to reflect the current body of evidence.

Current literature suggests a therapeutic benefit in implementing health recommendation guidelines for sunlight exposure during pregnancy [9], [13]. Nonetheless, it is necessary for policy recommendations to be developed after consultation with an interdisciplinary collaborative of atmospheric science experts, healthcare professional, medical scientists, public health officials, and policymakers. Due to geographical variations in sunlight exposure, recommendations should be designed at the provincial or regional level considering for the intensity, duration, and other anticipated meteorological factors.

Reported associations between timing of exposures and positive birth outcomes, suggest policies should target interventions could be useful in the second and third trimester. The second trimester marks the beginning of lung development and production of surfactant. Wernerfelt et al. suggested sunlight exposure during the second trimester could lead to a reduced risk for the development of asthma in later life [14]. This is conceivable as surfactant dysfunction is a risk factor for chronic airway inflammation, a signature of asthma. Similarly, interventions in the third trimester may be essential to lowering the risk of pneumonia [15], as it is the stage when key developmental events for normal lung development occur. There were also effects described in the third trimester [16], when skeletal development events are occurring in the fetus and the presence of UV-induced maternal vitamin D could be required. By targeting sunlight exposure interventions for these time points, it may be possible to ensure healthy developmental trajectories during pregnancy.

Next, epidemiological factors such as setting, time, and demographics must also be considered. Meteorological differences in Northern continents can affect levels of exposure received, when compared to Southern latitude countries. In fact, Canadian cities, such as Iqaluit, have average hours of sunlight reach lows of 0.4 hours per day as well as an average UV index of 0 in the winter months [17]. There are also racial, socioeconomic, and geographical differences, as observed in the study by Thayer et al. [18]. In this study, in addition to a higher birth outcomes in those living in the North compared to the South, there was a lower incidence of low BW and prematurity observed for non-Hispanic black women compared to non-Hispanic Caucasian women. Ngueta et al. hypothesize these outcomes may not directly be linked to racial differences but rely instead on the closely associated maternal fat mass [19]. According to this hypothesis, there is a lower bioavailability of vitamin D due to its lipophilicity, which causes it to be trapped in fat masses and unable to act to prevent adverse birth outcomes. Policies must therefore accommodate these genetic differences.

Ultimately, these individual-level differences are particularly important in multicultural and diverse countries such as Canada, where policy must make considerations for social determinants of health. Moreover, with varying exposures to sunlight in different regions coupled with differing methodologies to measure exposure effects in settings with a range of resource availabilities, it becomes difficult to make inferences about UV exposure without intricate epidemiological analysis. With genetic differences between ethnicities, individual behavioral differences, and distinctive exposure responses and capacities, another layer of complexity is added and must be accounted for when designing public health policies and recommendations. This also suggests interventions must be more personalized rather than assuming a one-size fits all strategy.