Mối tương quan giữa biến đổi khí hậu và tỷ lệ giới tính trẻ sơ sinh trong giai đoạn 2008 2016

VIETNAM NATIONAL UNVERSITY SCHOOL OF INTERDISCIPLINARY STUDIES NGUYEN THI VAN ASSOCIATION BETWEEN CLIMATE CHANGE AND MALE FEMALE RATIOS OF NEWBORN IN HANOI DURING THE PERIOD OF 2008 - 2016 GRADUATION MASTER THESIS IN CLIMATE CHANGE Hanoi - 2018 VIETNAM NATIONAL UNVERSITY SCHOOL OF INTERDISCIPLINARY STUDIES NGUYEN THI VAN ASSOCIATION BETWEEN CLIMATE CHANGE AND MALE FEMALE RATIOS OF NEWBORN IN HANOI DURING THE PERIOD OF 2008 - 2016 GRADUATION MASTER THESIS IN CLIMATE CHANGE Major: Climate change Code: Pilot program Supervisor: Assoc Prof., Dr Mai Van Hung Hanoi - 2018 DECLARATION I hereby declare that the thesis entitles “association between climate change and sex ratio of newborn in Hanoi during the period of 2008 – 2016” submitted for the completion of the master degree in the VNU School of Interdisciplinary Studies, Vietnam National University, Hanoi, Vietnam and the results therein are my own personal original, research work carried out under the guidance of Assoc Prof Dr Mai Van Hung and Dr Misao Fukuda All of the materials or data, which were in the course of this study, have been duty acknowledged by way of bibliography All references have been done legally, according to regulations of the VNU SGS The work included in this thesis is original and has not been submitted for any other publication Researcher Nguyen Thi Van ACKNOWLEDGEMENTS First of all, I would like to express my sincerest thanks to my supervisor, Associate Professor Doctor Mai Van Hung who shared his invaluable knowledge and experiences so openly and candidly to guide and encourage me to fulfill the study It must to say, I am so grateful for his great patience, persistence and understanding to follow my tough schedule during research implementation Thank you Doctor Misao Fukuda for inspiring me, supporting me with method and materials despite we have never met each other before Without them, none of this study would be done I am privileged to extend my sincere gratitude to Dr Luu Bich Ngoc who contributed precious ideas in order to fill the gap and improve the study Thanks to Dr Nguyen Trong An, MD, former Deputy Director of Department of Child Affairs (Ministry of Labor, Invalids and Social Affairs), Mr Nguyen Dai Duong, Head of the Organization and Administration Department (Hanoi Population and Family planning branch), Ms Nguyen Thuy Linh, Hanoi Department of Health, I could access raw data of yearly and monthly live births by gender (male and female) in Hanoi from 2008 to 2006 after my almost 1,5-year-effort in vain I would like to express my special thanks to Mr Nguyen Quang Ha, Chief of Office of National Hydrometeorology Center and my classmate as well, provided me with the record of temperature of Hanoi from 2007 to 2016 My appreciation to all professors of the master programs for providing us with informative lectures and sharing their practical experiences and Department of Training Management and Student Affairs, especially Dr Du Duc Thang, for the kindness and assistance Last but not least, my warmest thanks must be to my amazing family, boyfriend, friends for their love, constant encouragement so that I could complete the study CONTENT LIST OF TABLES i LIST OF FIGURES ii GLOSSARY INTRODUCTION .4 Rationale of the study Research question Patients and scope of the study Limitations Thesis structure 11 CHAPTER 1: BACKGROUND .12 1.1 Factors affecting male to female ratios of newborn .12 1.2 Climate change and the secondary sex ratio 25 2.1 Global warming & climate extremes 29 2.2 Data Analysis 33 CHAPTER 3: RESULTS AND DISCUSSION 35 3.1 Correlation between yearly mean temperature differences (0C) and male to female ratios of births from 2008 to 2016 35 3.2 Correlation between monthly mean temperature differences (0C) and male to female ratios of births from 2008 to 2016 39 CONCLUSION 43 RECOMMENDATION 44 LIST OF TABLES Table Sex ratios at age by province and urban or rural residence in Vietnam 22 Table Sex ratios of live births by parity in hospital data from Hanoi and Ho Chi Minh City 23 Table Monthly and yearly mean temperature differences in Hanoi from 2008 to 2009 31 Table Monthly and yearly male to female ratios at births in Hanoi from 2008 to 2016 32 i LIST OF FIGURES Figure Pearson correlation coefficient (r) between yearly mean temperature differences and male to female ratios (sex ratios) at births of Hanoi from 2008 to 2016 35 Figure Yearly mean temperature differences (0C) and male to female ratios of births (sex ratios at births) from 2008 to 2016 in Hanoi 36 Figure Pearson correlation coefficient (r) between monthly mean temperature differences in 2015 and sex ratios at births in months later 39 Figure Monthly mean temperature differences (0C) in 2015 and male to female ratios of births (sex ratios at births) from October 2015 to September 2016, months after the previous temperature assessment 41 ii GLOSSARY The sex ratio at birth refers to the number of boys born alive per 100 girls born alive (Handbook of Vital Statistics Systems and Methods, 1991) In other words, it is male female ratio of newborn In addition, the secondary sex ratio is defined as the ratio of male-to-female live births (United Nations DoEaSA, 2011) Therefore, in the present study, these three phrases were used alternatively together Climate change is a change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer Global warming is a phenomenon believed to occur as a result of the build—up of carbon dioxide and other greenhouse gases It has been identified by many scientists as a major global environmental threat (Glossary of Environment Statistics, 1997) Mean temperature difference or temperature anomaly means a departure from a reference value or long-term average A positive anomaly indicates that the observed temperature was warmer than the reference value, while a negative anomaly indicates that the observed temperature was cooler than the reference value It is calculated by the sum of monthly mean temperature minus the mean temperature during the previous years for the same month/12 (Fukuda at el., 2014) INTRODUCTION Rationale of the study a Climate change- a widespread phenomenon has massive negative impacts on human beings ―Summers to get hotter,‖ ―Climate change ―kills‖ 4000 people and ―digests‖ 1200 billion dollars,‖ ―Global Warming Seen as Security Threat,‖ ―Global warming a bigger threat to poor,‖ ―Tibet’s glacier’s heading for meltdown,‖ ―Climate change affects deep sea life,‖ ―More than half a million could die as climate change impacts diet – report‖, ―February breaks global temperature records by 'shocking' amount.‖ These are just a few of the many headlines that crossed the wires in 2016, and they have elicited widespread concern Scientific evidence for warming of the climate system is unequivocal - Intergovernmental Panel on Climate Change (IPCC) The Earth’s average surface temperature has risen by 0.76° C since 1850 (IPCC, 2007) In its Fourth Assessment Report projects that, the global average surface temperature is likely to rise by a further 1.8 - 4.0°C this century, and by up to 6.4°C in the worst case scenario Even the lower end of this range would take the temperature increase since pre-industrial times above 2°C – the threshold beyond which irreversible and possibly catastrophic changes become far more likely The climate change can affect every person and our health directly through increases in temperature Although it is undeniable that global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative (World Health Organization, 2015) Between 2000-2100, the heat related deaths will rise by 150,000 (Environmental Protection Agency, 2004) Such increases may lead to more extreme heat waves during the summer while producing less extreme cold spells during the winter Particular segments of the population such as those with heart problems, asthma, the elderly, and the very young can be especially vulnerable to extreme heat There can be extreme floods and droughts, hurricanes In 1877, a strong El Nino event caused failure of the monsoon rains in south and central India which resulted in the intense famine of to 10 million deaths due to the drought (World Health Organization, 2003) The El Nino effect on disasters is strong enough to be apparent at the global level (Bouma, M.J et al., 1997) In addition to natural disasters, climate change can have devastating effects on human societies with disease outbreaks (World Health Organization, 2003) Increase in temperature reduce the time taken for vector populations to breed and the incubation period of the pathogen (e.g malaria parasite, dengue or yellow fever virus) meaning that vectors become infectious more quickly (ISSN, 2013) Over 2.5 billion people are at risk, and there are estimated to be 0.5 billion cases and more than million deaths from malaria per year (World Health Organization, 1998) In 1996, Currents of change: El Nino’s impact on climate and society, Lien and Ninh found that the number of dengue cased increased in El Nino years In July 1995 a heat wave in Chicago, USA, caused 514 heat-related deaths (12 per 100 000 population) and 3300 excess emergency admission (Whitman et al., 1997) The morgues were full and bodies had to be stored in refrigerated trucks From 10 to 20 July, daily temperatures ranged from 34-40oC, with the highest temperature on 13 July The maximum number of deaths occurred on 15 July (Dematte J.E et al., 1998) Following the Chicago heat wave in 1995, Semenza et al conducted an important study on victims who died during the climate extreme and controls who lived near the case, matched for age and neighborhood Individual risk factors for dying in the heat wave were identified: chronic illness; confined to bed; unable to take for themselves; isolated; without air conditioners A comparison of mortality rates in three heat waves in 1966 by age group, sex and ethnic group indicated that women and white people were at more risk (Bridger and Helfand, 1968) Similarly, the sex ratios of children born in Germany during the period 1946 – 1995 were reported to be affected by environmental temperatures by Lerchl in 1998 The higher environmental temperature was, the bigger proportions of boys made up However, it is interesting to note that both Finland and Germany have relative low average yearly temperatures (1961-1990) of 1.750C and 8.50C, respectively (Climatic Research Unit, 2011) According to World Bank, the highest monthly mean temperatures from 1961 – 1990 are 17.10C for Germany and 15.10C for Finland Compared to 27.50C for Vietnam and 22.90C for Japan, it must be mentioned, therefore, the ―warm years‖ are ―comfortable years‖ In addition, Grech et al presented a latitude gradient in Europe and Asia in 2002 and 2013, respectively, with more boys being born in southern, warmer latitudes (Grech et al., 2002; 2013) However, with the same method, Grech and his team failed to find the relationship between male to female ratio at birth and latitude in Australia and New Zealand from 1950 to 2010 However, the underlying mechanisms of negative correlation or positive correlation between two mentioned variables both remain unknown This might be associated with the action of both pre- and post- conception mechanisms of sex ratio variation (Jimenez et al., 2003) Temperature may influence primary sex determination by the variable fertilization success of X- and Y-bearing sperm (McLachlan & Storey 2003) In mammals, ambient temperature affects the steroid concentrations of ovarian follicles (Wolfenson et al 2000; De Rensis & Scaramuzzi 2003) and, for example, a high follicular testosterone concentration may be associated with the fertilized ovum being a male (Grant & Irwin 2005) Stressful environmental conditions may also impair sperm motility, potentially promoting female-biased birth sex ratio (Fukuda et al 1996, 1998; Gomendio et al 2006) In addition, a candidate may be air pollution that has suggested increasing preterm births (Sagiv et al., 2005) and decreasing sex ratios of births (Lichtenfels et al., 2007) Other candidates are toxic chemical exposure (Mocarelli et al., 1996) and methylmercury from the Minamata Bay disaster (Sakamoto et al., 2001) Our data cannot, 38 unfortunately, tell what mechanism(s) was responsible for these results, but the hypothesis was confirmed once again when I observed association of heat extreme 2015 with the secondary sex ratios in nine months later as below 3.2 Correlation between monthly mean temperature differences (0C) and male to female ratios of births from 2008 to 2016 From the table 1, we can realize that it was only the year of 2015 during the period to have experienced 11 months of positive temperature differences, except for December with relative small negative temperature difference of -0.12 Moreover, the temperature difference in May which was the biggest monthly temperature difference in 2015, was also the highest one over the period of 2008 to 2016 (2.02) A very significant negative correlation was found between monthly temperature differences in 2015 and monthly sex ratios at births in nine months later (r = 0.632, t = -2.158 < -1.82) (Figure 3) Figure Pearson correlation coefficient (r) between monthly mean temperature differences in 2015 and sex ratios at births in months later 39 These calculations were performed using nine months interval between temperature differences and sex ratios of births However, the significance disappeared, when the intervals was shortens from nine to eight months (r = -0.158, t = -0.498), to seven months (t= -0.371, t = -1.057), to six months (r = -0.143, t = -0.382), to five months (r = -0.063, t = -0.167), to four months (r = -0.401, t = -1.158), to three months (r = -0.094, t = -0.25), to two months (r = 0.158, t = 0.423), to one month (r = 0.158, t = 0.423), and to zero month (r = 0.61, t = 1.408) All those Pearson correlation coefficients (r) are pretty small or/and t values are bigger than -1.82 and small than 1.82, which implied that the most appropriate interval is nine months, which supported Fukuda’s argument when he found the best correlation between absolute temperature assessment and sex ratios of births with a nine month interval 40 Montly mean temperature difference in 2015 Monthly mean temperature difference in 2015 Figure Monthly mean temperature differences (0C) in 2015 and male to female ratios of births (sex ratios at births) from October 2015 to September 2016, months after the previous temperature assessment The figure showed the trends of the monthly temperature differences in 2015 and male:female ratios from October, 2015 to September 2016 ( a month interval) They were approximate opposite each other While the temperature difference hit 41 the lowest points in April and from June to September in 2015, the sex ratio at births reached the highest levels in January and from April to June in 2016 Similarly, the peaks of the temperature difference in January and November in 2015 were relevant to smallest secondary sex ratios in October, 2015 and August, 2016 However, the sex ratio of newborns in February, 2016 was pretty high although the temperature difference in previous months (in May, 2015) was the biggest It can be explained that global warming is not exclusive factor of sex ratios at births which can be impacted by many different determinants such as pollution, parental age, diet, psychological stress, economics status, … 42 CONCLUSION Using the method of Fukuda and his team, I have tested a possible association between men temperature differences and male to female ratios of newborn in Hanoi during the period of 2008 – 2016 in two different ways: (i) As a long-term, we found a significant negative correlation between mean temperature difference and sex ratios of live births The bigger difference yearly mean temperature had the smaller male to female ratios of children born in Hanoi since 2008 (ii) As a short-term, monthly mean temperature difference in the hottest year 2015 had closely negative correlation with sex ratios at birth in months later, from October 2015 to September 2016 Collectively, average surface temperature increase – a key climate indicator, have been associated with sex ratios of newborn in Hanoi during the period 2008 – 2016 It was likely that fewer boys were born in the hot years and male to female ratio at birth dropped dramatically months later since the extremely hot month occurred 43 RECOMMENDATION The underlying mechanisms of declines in sex ratios at birth may be partially caused of increase in male fetal deaths related to fertilization of XY embryos by reduced motility of healthy Y spermatozoa which may injure from external stress factors including climate changes Unfortunately, the study cannot provide with clear explanation of the mentioned phenomenon Therefore, further investigations with experimental demonstrations are needed to clarify the phenomenon and evaluate how global warming may affect the male to female of newborn The study cannot provide a complete and measurable picture of the situation across the country because of limited database Hence, in-depth censuses conducted for both Hanoi (4-season weather) and Ho Chi Minh (2-season weather) is necessary and valuable In addition, I highly recommend a research to assess the association between climate warming and sex ratio at birth before 2009 when the imbalance of newborn infant sex ratio was officially acknowledged in order to confirm the influence of son preference and provided a comprehensive assessment of the correlation between the sex ratio at birth and climate change in Hanoi We know that warming and cooling have happened in the past, and long before humans were around Natural factors can influence Erath’s climate – such as changes in the sun’s intensity and volcanic eruptions, as well as heat-trapping gases in the atmosphere However, IPCC in 2013 reported that ―human-emitted greenhouse gases are extremely likely (at least 95% chance) responsible for more than half of Earth’s temperature increase since 1951” Therefore, that climate change harms human society, particularly reproductive health has been investigated in Hanoi, Vietnam, which alarms and fosters people there to take actions to slow down climate change and protect environment 44 REFERENCES Allan, B.B., Brant, R., Seidel, J.E., Farrell, J.F (1997) Declining sex ratios in Canada Can Med Assoc J Askling, J., Erlandsson, G., KaiJser, A O., Ekbom, A (1999) Hyperemesis gravidarum and sex of child Lancet Bouma, M.J, Kovats, R.S., Goubet, S.A., Cox, J.S., Haines, A (1997) Global assessment of El Niño's disaster burden Lancet Bromen, K., Jockel, K.H Change in male proportion among newborn Lancet Bridger, C.A & Helfand, L.A (1968) Mortality from heat during July 1966 in Illinois.International Journal of Biometeorology Cagnacci, A., Renzi, A., Arangino, S., Alessandrini, C., Volpe, A (2003) The male disadvantage and the seasonal rhythm of sex ratio at the time of conception Hum Reprod Clara, T., Anna, L Choi, Maria, S.P., Flemming N., Esben, B.J., Pál, W., Philippe, G.(2017) Secondary sex ratio in relation to exposures to polychlorinated biphenyls, dichlorodiphenyl dichloroethylene and methylmercury International Journal of Circumpolar Health Davis, D.L., Gottlieb, M.B., Stampnitzky, J.R (1998) Reduced ratio of male to femalebirths in industrial countries: a sentinel health indicator? JAMA D'Alfonso, A., Patacchiola, F., Colagrande, I., D'Alfonso, G., Di Fonso, A., Palermo, P (2012) Decrease in sex ratio at birth nine months after the earthquake in L'Aquila Scientific World 10 Dematte, J.E., O’Mara, K., Buescher, J (1998) Near-fatal heat stroke during the 1995 heat wave in Chicago Ann Intern Med 45 11 Dixson, B.J., Haywood, J., Lester, P.J., Ormsby, D.K (2011) Whatever the weather:ambient temperature does not influence the proportion of males born in New Zealand PLoS One 12 Dickinson, H.O., Parker, L (1996) Why is the sex ratio falling in England and Wales? JEpidemiol Commun Healt 13 Doger, E., Cakıroglu, Y., Köpük, S.Y., Ceylan Y, Simsek, H.U., Calıskan, E (2013) Impact of earthquakes on sex ratio at birth: Eastern Marmara earthquakes J Turk Ger Gynecol Assoc 14 Dorthe, H., Henrik, M., Jørn, O (1999) Severe periconceptional life events and the sex ratio in offspring: follow up study based on five national registers.BMJ 15 Fukuda, M., Shimizu, T., Andersen, C.Y (2015) Climate change, Tohoku of earthquake asn sex ratio of fetal death & birth.LAP LAMBERT 16 Fukuda, M., Fukuda, K., Shimizu, T., Nobunaga, M., Mamsen, L.S., Andersen, C.Y (2014) Climate change is associated with male:female ratios of fetal deaths and newborn infants in Japan 17 Fukuda, M., Fukuda, K., Shimizu, T., Andersen, C.Y., Byskov, A.G (2002) Parental periconceptional smoking and male:female ratio of newborn Lancet 18 Fukuda, M., Fukuda, K., Shimizu, T., Andersen, C.Y., Byskov, A.G (2003) Periconceptional smoking and the male to female ratio in the offspring – reassessment of a recently proposed hypothesis Int J Epidemiol 19 Fukuda, M., Fukuda, K., Shimizu, T., Møller, H (1998) Decline in sex ratio at birth afterKobe earthquake Hum Reprod 20 Fukuda, M., Fukuda, K., Shimizu, T., Nobunaga, M., Byskov, A.G., Yding, A C (2011) The sex ratio of offspring is associated with the mother’s age at menarche Hum Reprod 46 21 James W.H (2000) Hyperemesis gravidarum and sex of child Lancet 22 James, W.H (1995) Sex ratios of offspring and the causes of placental Pathology Hum Reprod 23 Janzen, F.J (1994) Climate change and temperature-dependent sex determination in reptiles Proc Natl Acad Sci 24 James, W.H (1994) Cycle day of insemination, sex ratio of offspring and duration of gestation Ann Hum Biol 25 Jongbloet, P.H., Groenewoud, J.M.M., Zielhuis, G.A (1996) Non-optimal maturation of oocytes and the sex ratio Hum Reprod 26 Glossary of Environment Statistics (1997) Studies in Methods Series F, No 67, United Nations, New York 27 Grech, V., Vassallo-Agius, P., Savona-Ventura C Declining male births with increasing geographical latitude in Europe J Epidemiol Commun Health 2000;54:244–6 28 Grech, V (2013) Secular trends and latitude gradients in sex ratio at birth in Asia during the past 60 years Pediatr Int 29 Grech, V., Scherb, H (2015) Hurricane Katrina: Influence on the Male-toFemale Birth Ratio Med Princ Pract 30 Helle, S., Helama, S., Lertola, K (2009) Evolutionary ecology of human birth sex ratiounder the compound influence of climate change, famine, economic crises and wars J Anim Ecol 31 Helle, S., Helama, S., Jokela, J (2008) Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons Biol Lett 47 32 Handbook of Vital Statistics Systems and Methods (1991) Volume 1: Legal, Organisational and Technical Aspects, United Nations Studies in Methods, Glossary, Series F, No 35, United Nations, New York 33 International Journal of Humanities and Social Science Invention ISSN (2013) (Online): 2319 – 7722, ISSN (Print): 2319 – 7714 www.ijhssi.org Volume Issue ǁ March 2013ǁ PP.31-39 34 Kalkstein, L.S., Greene, J.S (1997) An evaluation of climate/mortality relationships in large U.S cities and the possible impacts of a climate change Environ Health Perspect 35 Krackow, S (1995) Potential mechanisms for sex ratio adjustment in mammals and birds Biol Rev Camb Philos Soc 36 Krackow, S., Burgoyne, P.S (1998) Timing of mating, developmental asynchrony and the sex ratio in mice Physiol Behav 37 Lerchl, A (1999) Sex ratios at birth and environmental temperatures Naturwissenschaften 38 Lerchl, A (1998a) Changes in the seasonality of mortality in Germany from 1946 to 1995:the role of temperature Int J Biometeorol 39 Lerchl, A (1998b) Seasonality of sex ratio in Germany Hum Reprod 40 Lyster, W.R (1974) Altered sex ratio after the London smog of 1952 and the Brisbane flood of 1965 J Obstet Gynaecol Br Commonw 41 Mackensie, C.,Lockridge, A., Keith, M (2005) Declining sex ratio in a first nation community Environment health perspectives 42 Møller, H (1996) Change in male: female ratio among newborn in Denmark Lancet 43 Møller, H (1998) Trends in sex-ratio, testicular cancer and male reproductive hazards: are they connected? Acta Pathol Microbiol Immunol Scand 48 44 Mocarelli, P., Brambilla,P., Gerthoux, P.M., Patterson Jr., D.G., Needham, L.L (1996) Change in sex ratio with exposure to dioxin Lancet 45 Mittwoch, U (1996) Differential implantation rates and variations in the sex ratio Hum Reprod 46 Parazzini, F., La, V C., Levi, F., Franceschi, S (1998) Trends in male:female ratioamong newborn in 29 countries from five continents Hum Reprod 47 Torche, F., Kleinhaus, K (2012) Prenatal stress, gestational age and secondary sex ratio: the sex-specific effects of exposure to a natural disaster in early pregnancy Hum Reprod 48 Saadat, M (2008) Decline in sex ratio at birth after Bam (Kerman Province, SouthernIran) earthquake J Biosoc Sci 49 United Nations DoEaSA, Population Division (2011) World Population Prospects: The 2010 Revision New York 50 Van der Pal-deBruin, K.M., Verloove-Vanhorick, S.P., Roeleveld, N (1997) Change inmale:female ratio among newborn babies in Netherlands Lancet 51 Whitman, S., Good, G., Donoghue, E.R., Benbow, Nanette, Shou, WY & Mou, Sam (1997) Mortality in Chicago attributed to the July 1995 heat wave American journal of public health 87 1515-8 10.2105/AJPH.87.9.1515 52 Conserve Energy Future (2014) 35 Surprising Facts About Global Warming Retrieved from: https://www.conserve-energy-future.com/various-global- warming-facts.php 53 Yorifuji, T., Kashima, S (2016) Secondary sex ratio in regions severely exposed to methylmercury “Minamata disease” Int Arch Occup Environ Health 49 54 Helle, S., Helama, S (2007) Climatic variability and the population dynamics of historical hunter-gatherers: the case of Sami of northern Finland Am J Hum Biol 55 Bélanger Danièle, Khuat T H O., Liu J., Le Thanh Thuy, Pham Viet Thanh Are Sex Ratios at Birth Increasing in Vietnam? In: Population (English edition), 58ᵉ année, n°2, 2003 pp 231-250; http://www.persee.fr/doc/pop_1634-2941_2003_num_58_2_18440 56 Bongaarts, J (2013), The Implementation of Preferences for Male Offspring Retrieved from: http://onlinelibrary.wiley.com/doi/10.1111/j.1728- 4457.2013.00588.x/full 57 Caitlyn, K.C., Lindsey, R (2015) What's the difference between global warming and climate change Retrieved from: https://www.climate.gov/newsfeatures/climate-qa/whats-difference-between-global-warming-and-climatechange 58 Catalano, R., Brucker, T., Smith, R (2007) Ambient temperature predicts sex ratios and male longevity Retrieved from: http://www.pnas.org/content/105/6/2244.full 59 Cnattingius, S., Haglund, B., Sci, M (1997) Decreaseing smoking prevalence during pregnancy in Sweden: The effect on small for gestational age births Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1381013/pdf/amjph005020092.pdf 60 General Statistics Office (2012) Statistical yearbook of 2009 Retrieved from: http://www.gso.gov.vn/default.aspx?tabid=387&idmid=3&ItemID=9860 cited 19 September 2012 50 61 Guilmoto, C., Hoang, X., Ngo, T (2009) Recent increase in Sex ratio at birth in Vietnam Retrieved from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004624 62 Guilmoto, C (2007) Sex-ratio imbalance in Asian: trends, consequenses and policy responsese Retrieved from: https://www.unfpa.org/sites/default/files/resource-pdf/regional_analysis.pdf\ 63 IPCC Fourth Assessment Report: Climate Change (2007) Retrieved from: https://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-3-1-1.html 64 Intergovernmental Panel on Climate Change (IPCC) (2012) Glossary of Terms Oxford Dictionaries Retrieved from: http://oxforddictionaries.com/definition/english/climate%2Bchange 65 Martin, F and Andreas, K (2014) Droughts and Gender Bias in Infant Mortality in Sub-Saharan Africa Department of Economics University of Oslo 2014 Retrieved from https://www.sv.uio.no/econ/english/research/unpublishedworks/working-papers/pdf-files/2014/memo-02-2014.pdf 66 Strauss, B H., Kulp, S., Levermann, A (2015) Carbon choices determine US cities committed to futures below sea level Proceedings of the National Academy of Sciences of the United States of America Retrieved from: http://www.pnas.org/cgi/doi/10.1073/pnas.1511186112 67 United States Environmental Protection Agency Climate change and the health of pregnant women Retrieved from: https://www.cmu.edu/steinbrenner/EPA%20Factsheets/pregnant-healthclimate-change.pdf 68 UNFPA 2011 Son Preference in Viet Nam: Ancient Desires, Advancing Technologies Qualitative research report to Better Understand the rapidly rising Sex ratio at Birth in Viet Nam, United Nations Fund for Population, Ha Noi; http://tinyurl.com/cugvk8a 51 69 Valentine Becquet and Christophe Z Guilmoto (2013) Sex selection and family patterns across Vietnam Retrieved from: https://iias.asia/sites/default/files/IIAS_NL64_44.pdf 70 World Health Organization (2017) Climate change and health Retrieved from: http://www.who.int/mediacentre/factsheets/fs266/en/ 71 World Health Organization (2003) Climate change and human health- Risks and responses Retrieved from: http://www.who.int/globalchange/publications/climchange.pdf 52 ... female ratios of births from 2008 to 2016 35 3.2 Correlation between monthly mean temperature differences (0C) and male to female ratios of births from 2008 to 2016 39 CONCLUSION... births of Hanoi from 2008 to 2016 35 Figure Yearly mean temperature differences (0C) and male to female ratios of births (sex ratios at births) from 2008 to 2016 in Hanoi 36... perceptions of climate change and its effect on sex ratio of birth during the last years, 2008 - 2016 2008- 2016 I supposed to conduct observation and assessment of the probable relationship between