==== Front J Family Med Prim CareJ Family Med Prim CareJFMPCJournal of Family Medicine and Primary Care2249-48632278-7135Medknow Publications & Media Pvt Ltd India JFMPC-7-51110.4103/jfmpc.jfmpc_311_17Review ArticleUltraviolet radiation and its effects on pregnancy: A review study Botyar Malihe 1Khoramroudi Rozita 11 Department of Midwifery, Tehran, IranAddress for correspondence: Dr. Rozita Khoramroudi, Department of Midwifery, Iran University of Medical Sciences, Tehran, Iran E-mail: rozkhoram@yahoo.comMay-Jun 2018 7 3 511 514 Copyright: © 2018 Journal of Family Medicine and Primary Care2018This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.Seasons and Vitamin D are factors that are directly and indirectly related to ultraviolet (UV) radiations and can affect pregnancy. Therefore, the present study aims at investigating the effects of being exposed to direct UV radiation during pregnancy period and its effects on fetal growth, premature birth, and high blood pressure. This study was conducted by searching different websites such as Medline, Embase, ProQuest, Global Health, Google Scholar, and Scopus. Of the 430 papers found, between 1985 and 2017, seventeen related articles were used. The results showed that being exposed to UV radiation during the first 3 months of pregnancy is associated with improved fetal growth and causes high blood pressure during pregnancy. The literature shows that being women exposure to UV radiation had beneficial effects on fetal growth and blood pressure during pregnancy period. However, since this issue has not been extensively studied in the past, the results from previous studies should be generalized with extreme care and caution. Therefore, it is suggested that further studies be carried out in this area. Fetal growthgynecologypregnancyultraviolet radiation ==== Body Introduction Proper development and growth of the fetus and the presence of diseases is related to weight at birth, the length of pregnancy, and geographical location.[123] A significant relationship has been found between premature birth, low birth weight at birth, and season with the immune system, infections, Vitamin D, and hormone paths.[45] Meteorologically, using different seasons as a variable has some special limitations. Seasons are not just a meteorological phenomenon, but they are related to psychological, biological, and behavioral effects, and it also affects ovulation rate and pregnancy.[6] Although the relationship between pregnancy and seasons is interesting, it is the ultraviolet (UV) radiation that plays the main role in seasons and its amount is variable and different in different seasons.[78] UV radiation is classified into the three spectrums, i.e., A, B, and C. The whole UV spectrum varies from 290 to 400 nanometers. The A spectrum varies from 315 to 400 nanometers and B from 290 to 315 nanometers. The determinants of being exposed to UV radiation are as follows: how the sun shines toward the earth, calendar time and date, altitude of the geographic location, degree of cloud coverage, and being close to coasts. People's behavioral factors can also determine the effectiveness of UV radiation. These factors include how people dress, the amount of time spent outside the home, and using sunscreen.[9] The mortality rate associated with cardiovascular diseases in adults who are less exposed to the sunlight is higher in winter and in high places.[10111213] Increasing UV exposure during pregnancy is associated with an increase in MS and schizophrenia in adult children.[14] Palacios et al. and Wei et al. in two separate meta-analysis studies showed that lack of vitamin D which is a main indicators of being less exposed to the sunlight is related to low eight at birth, premature birth, preeclampsia (pregnancy poisoning), and pregnancy diabetes.[1516] There are also reliable biological paths that support the relationship between the results of UV radiation and pregnancy, which are independent of Vitamin D path. For example, clinical studies have shown that sunlight, especially UVA, has direct effects on vascular health and reduces blood pressure through the release of nitric oxide from the skin.[17] Being exposed to UVA for 20 min causes a 3.5 mmHg reduction in the average systolic arterial pressure and 4.9 mmHg in the diastolic blood pressure in healthy adults.[17] In the animal sample, the beneficial effects of UVA exposure on the immune system and metabolic systems have been confirmed. When exposed to UV radiation, the weight of mice fed with high-fat diets was 40% lower and had fewer metabolic disorders and less fasting glucose, insulin, and glucose intolerance.[18] In the present study, it is assumed that UV radiation can affect pregnancy. Therefore, the objective is to review the literature on the relationship between UV radiation and the results of pregnancy, including weight at birth, the length of pregnancy, premature birth, and high blood pressure complications. Methods We take into consideration those studies in which exposure to sunlight has been reported. These measurements include direct and indirect exposure to sunlight and UV radiation. These studies were conducted from 1985 to 2017. In the present study, the search was done in different websites such as Medline, Embase, ProQuest, Global Health, Google Scholar, and Scopus. Of the 430 papers found, between 1985 and 2017, seventeen related articles were used. Results The effect of being exposed to ultraviolet radiation on the growth of the fetus Five studies showed that UV radiation exposure has positive effects on fetal growth. All these studies used government information system at birth to determine these effects. Three studies directly investigated weight at birth.[192021] and two studies considered the length of pregnancy.[2223] Different methods had been considered to measure UV radiation and the duration of exposure. The incidence of low weight at birth (<2500 g) and its correlation with average annual UV index was investigated by Thayer in a cross-sectional study in America. The results showed that higher average annual UV index was related to lower birth weight. Tustin et al. and Waldie et al. both reported the relationship between average birth weight and average hours of sunlight exposure and found a positive correlation between exposure to sunlight and weight in the first 3 months.[2021] Waldie et al. used spectrum analysis to compare average monthly birth weight fluctuations with average monthly sunlight fluctuations and showed that, in the pattern of these fluctuations, the peak of birth weight is related to the peak of sunlight during the first 3 months of pregnancy.[21] Tustin et al. tested exposure to sunlight during the first 3 months of pregnancy as a hypothesis. They investigated 903 births who had been exposed to sunlight at peak hours of radiation during the first 3 months of pregnancy and observed a 67.9 g increase (P < 0.05) in weight at birth.[20] Pereira et al. and Walter (2004), however, did not find a significant relationship between exposure to sunlight during the whole period of pregnancy and weight after birth.[23] Premature delivery and ultraviolet radiation A relationship between pregnancy length and UV has been reported in only one study in 2007. Thayer investigated the relationship between UV and premature delivery rate in America. Methodologically, the study was similar to the study conducted on low weight birth.[19] Similarly, they found that premature delivery both in white and black women increases as average annual UV index increases.[19] A positive relationship was found between state UV index and poverty factors that limit the applications of these results.[19] High blood pressure and ultraviolet radiation Only two studies investigated the relationship between pregnancy high blood pressure complications and UV, and they assumed that the peak of exposure to sunlight during the first 3 months of pregnancy is critical in causing complications associated with high blood pressure. Algert et al. reviewed a study in Australia which had investigated 424,732 births. Further exposure to sunlight during the first 3 months and less exposure to sunlight in the third 3 months are strongly related to the risk of pregnancy high blood pressure.[24] Tran et al. reviewed a comprehensive study in France that had investigated 63,000 births and in which the incidence of acute preeclampsia (pregnancy poisoning) was 526 cases. During the first 3 months of pregnancy, high exposure to UV radiation increases acute preeclampsia but not significantly.[25] Both studies used direct regional government measurement of UV in sunlight in Megajoule (MJ) per square meter for the time period of first 3 months of pregnancy. Algert (2010) used a region but Tran used the daily average of the two regions[2425] Conclusions The present study is a review of the effects of UV radiation on birth consequences and pregnancy complications. Despite the importance of such a study, few studies were available to be able to extract more general results. Despite the scarcity of studies in the area, the studies showed that exposure to UV during the first 3 months of pregnancy is beneficial for the growth of the fetus. On the other hand, UV radiation causes pregnancy blood pressure to increase. In the present review, the effects on fetal growth due to exposure to UV are not contradictory, but methodological limitations force us to apply the results with extreme care and caution. Fetal growth may be affected by exposure to UV radiation, and the review studies by Pérez-López et al. and Wei et al. lend support to the conclusion. In their review studies, the data for Vitamin D and pregnancy showed similar relationships between early and mid-pregnancy defects and fetal growth limitations.[1626] The two studies conducted in New Zealand showed beneficial effects for exposure to UV in the first 3 months of pregnancy, while neither Elter (2004) nor Pereira et al. reported these beneficial effects in areas with low altitudes in the two countries of Turkey and Australia.[20212223] Regarding cardiovascular complications and diseases in adults, the effects of UV have been identified. Less exposure to UV causes high blood pressure in people.[11272829] High blood pressure in common among 10% of pregnant women, and it is an important and significant factor in infants and mother mortality rates.[30] Nitric oxide path has been identified by Liu (2014). During exposure to UV, nitric oxide is released from the skin, and nitric oxide is a central signal for vascular compatibility and also causes the growth of the fetus during pregnancy.[3132] Nitrate donors such as L-arginine, sildenafil, and isosorbide mononitrate are used in clinical cases to prevent preeclampsia in fetal growth limitation.[3334] Less exposure to in the third 3 months of pregnancy is associated with pregnancy high blood pressure.[2425] Conclusions Optimizing pregnancy conditions is vital to the health of future generations. Sunlight is considered an important environmental variable in eliminating public health worries since Vitamin D supplement tests during pregnancy continue to show negative effects on pregnancy. This review study showed the effects of UV radiation on pregnancy consequences in 7 studies, and exposure to UV radiation was found to be an explanatory variable. Few studies and little evidence exist in support of the effects of UV exposure on pregnancy. Therefore, it is suggested that further studies be conducted, so that their results can be used with a higher degree of certainty. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. ==== Refs 1 Barker DJ The fetal and infant origins of disease Eur J Clin Invest 1995 25 457 63 7556362 2 Godfrey KM Barker DJ Fetal nutrition and adult disease Am J Clin Nutr 2000 71 1344S 52S 10799412 3 Barker DJ In utero programming of cardiovascular disease Theriogenology 2000 53 555 74 10735050 4 Beltran AJ Wu J Laurent O Associations of meteorology with adverse pregnancy outcomes: A systematic review of preeclampsia, preterm birth and birth weight Int J Environ Res Public Health 2013 11 91 172 24362545 5 Chodick G Flash S Deoitch Y Shalev V Seasonality in birth weight: Review of global patterns and potential causes Hum Biol 2009 81 463 77 20067370 6 Weinberg CR Shi M DeRoo LA Basso O Skjćrven R Season and preterm birth in Norway: A cautionary tale Int J Epidemiol 2015 44 1068 78 26045507 7 Porojnicu AC Lagunova Z Robsahm TE Berg JP Dahlback A Moan J Changes in risk of death from breast cancer with season and latitude: Sun exposure and breast cancer survival in Norway Breast Cancer Res Treat 2007 102 323 8 17028983 8 Lucas R McMichael T Smith W Armstrong BK Prüss-Üstün A Organization, W.H., Solar Ultraviolet Radiation: Global Burden of Disease from Solar Ultraviolet Radiation. (6) The Impact of Air pollutants, UV exposure and Geographic Location on Vitamin D deficiency 2006 accessed May 12 2018 Available from: https://www.researchgate.net/publication/322789988_The_Impact_of_Air_pollutants_UV_exposure_and_Geographic_Location_on_Vitamin_D_deficiency 9 Cherrie MP Wheeler BW White MP Sarran CE Osborne NJ Coastal climate is associated with elevated solar irradiance and higher 25(OH) D level Environ Int 2015 77 76 84 25660687 10 Brřndum-Jacobsen P Nordestgaard BG Nielsen SF Benn M Skin cancer as a marker of sun exposure associates with myocardial infarction, hip fracture and death from any cause Int J Epidemiol 2013 42 1486 96 24038635 11 Fares A Winter cardiovascular diseases phenomenon N Am J Med Sci 2013 5 266 79 23724401 12 Fleck A Latitude and ischaemic heart disease Lancet 1989 1 613 13 Wong A Incident solar radiation and coronary heart disease mortality rates in Europe Eur J Epidemiol 2008 23 609 14 18704704 14 Staples J Ponsonby AL Lim L Low maternal exposure to ultraviolet radiation in pregnancy, month of birth, and risk of multiple sclerosis in offspring: Longitudinal analysis BMJ 2010 340 c1640 21030361 15 Palacios C De-Regil LM Lombardo LK Peńa-Rosas JP Vitamin D supplementation during pregnancy: Updated meta-analysis on maternal outcomes J Steroid Biochem Mol Biol 2016 164 148 55 26877200 16 Wei SQ Qi HP Luo ZC Fraser WD Maternal Vitamin D status and adverse pregnancy outcomes: A systematic review and meta-analysis J Matern Fetal Neonatal Med 2013 26 889 99 23311886 17 Liu D Fernandez BO Hamilton A Lang NN Gallagher JMC Newby DE UVA irradiation of human skin vasodilates arterial vasculature and lowers blood pressure independently of nitric oxide synthase J Invest Dermatol 2014 134 1839 46 24445737 18 Geldenhuys S Hart PH Endersby R Jacoby P Feelisch M Weller RB Ultraviolet radiation suppresses obesity and symptoms of metabolic syndrome independently of Vitamin D in mice fed a high-fat diet Diabetes 2014 63 3759 69 25342734 19 Thayer ZM The Vitamin D hypothesis revisited: Race-based disparities in birth outcomes in the United States and ultraviolet light availability Am J Epidemiol 2014 179 947 55 24618066 20 Tustin K Gross J Hayne H Maternal exposure to first-trimester sunshine is associated with increased birth weight in human infants Dev Psychobiol 2004 45 221 30 15549686 21 Waldie KE Poulton R Kirk IJ Silva PA The effects of pre- and post-natal sunlight exposure on human growth: Evidence from the Southern Hemisphere Early Hum Dev 2000 60 35 42 11054582 22 Elter K Ay E Uyar E Kavak ZN Exposure to low outdoor temperature in the midtrimester is associated with low birth weight Aust N Z J Obstet Gynaecol 2004 44 553 7 15598296 23 Pereira G Cook A Haggar F Bower C Nassar N Seasonal variation in fetal growth: Accounting for sociodemographic, biological, and environmental exposures Am J Obstet Gynecol 2012 206 74.e1 7 21982022 24 Algert CS Roberts CL Shand AW Morris JM Ford JB Seasonal variation in pregnancy hypertension is correlated with sunlight intensity Am J Obstet Gynecol 2010 203 215.e1 5 20537304 25 Tran TC Boumendil A Bussieres L Lebreton E Ropers J Rozenberg P Are meteorological conditions within the first trimester of pregnancy associated with the risk of severe pre-eclampsia? Paediatr Perinat Epidemiol 2015 29 261 70 26053449 26 Pérez-López FR Pasupuleti V Mezones-Holguin E Benites-Zapata VA Thota P Deshpande A Effect of Vitamin D supplementation during pregnancy on maternal and neonatal outcomes: A systematic review and meta-analysis of randomized controlled trials Fertil Steril 2015 103 1278 88.e4 25813278 27 Hart PH Gorman S Finlay-Jones JJ Modulation of the immune system by UV radiation: More than just the effects of Vitamin D? Nat Rev Immunol 2011 11 584 96 21852793 28 Law MR Morris JK Why is mortality higher in poorer areas and in more Northern areas of England and wales? J Epidemiol Community Health 1998 52 344 52 9764254 29 Xu B Liu H Su N Kong G Bao X Li J Association between winter season and risk of death from cardiovascular diseases: A study in more than half a million inpatients in Beijing, China BMC Cardiovasc Disord 2013 13 93 24172216 30 Gongora MC Wenger NK Cardiovascular complications of pregnancy Int J Mol Sci 2015 16 23905 28 26473833 31 Leiva A Fuenzalida B Barros E Sobrevia B Salsoso R Sáez T Nitric oxide is a central common metabolite in vascular dysfunction associated with diseases of human pregnancy Curr Vasc Pharmacol 2016 14 237 59 26899560 32 Sladek SM Magness RR Conrad KP Nitric oxide and pregnancy Am J Physiol 1997 272 R441 63 9124465 33 Chan E Leong P Malouf R Quigley MA Long-term cognitive and school outcomes of late-preterm and early-term births: A systematic review Child Care Health Dev 2016 42 297 312 26860873 34 Johal T Lees CC Everett TR Wilkinson IB The nitric oxide pathway and possible therapeutic options in pre-eclampsia Br J Clin Pharmacol 2014 78 244 57 24313856