This study examines whether exposure to ambient temperature in nineteenth-century urban space affected the ratio of boys to girls at birth. Furthermore, we investigate the details of temperature effects timing upon sex ratio at birth. The research included 66,009 individual births, aggregated in subsequent months of births for the years 1847-1900, i.e. 33,922 boys and 32,087 girls. The statistical modelling of the probability of a girl being born is based on logistic GAM with penalized splines and automatically selected complexity. Our research emphasizes the significant effect of temperature in the year of conception: the higher the temperature was, the smaller probability of a girl being born was observed. There were also several significant temperature lags before conception and during pregnancy. Our findings indicate that in the past, ambient temperature, similar to psychological stress, hunger, malnutrition, and social and economic factors, influenced the viability of a foetus. Research on the effects of climate on the sex ratio in historical populations may allow for a better understanding of the relationship between environmental factors and reproduction, especially concerning historical populations since due to some cultural limitations, they were more prone to stronger environmental stressors than currently.

Department of Biostatistics National Institute of Public Health Prague Czech Republic

Department of Meteorology and Climatology Faculty of Geographic and Geological Sciences Adam Mickiewicz University Poznań Poland

Department of Statistical Modelling Institute of Computer Science The Czech Academy of Sciences Prague Czech Republic

Doctoral School of Humanities Adam Mickiewicz University Poznań Poland

Institute of Human Biology and Evolution Faculty of Biology Adam Mickiewicz University Poznań Poland

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Bonell A, Hirst J, Vicedo-Cabrera AM, Haines A, Prentice AM, Maxwell NS. A protocol for an observational cohort study of heat strain and its effect on fetal wellbeing in pregnant farmers in The Gambia. Wellcome Open Res. 2020;31(5):32. doi: 10.12688/wellcomeopenres.15731.2. PubMed DOI PMC

Rekha S, Nalini SJ, Bhuvana S, Kanmani S, Vidhya VA. Comprehensive review on hot ambient temperature and its impacts on adverse pregnancy outcomes. J. Mother Child. 2023;27(1):10–20. doi: 10.34763/jmotherandchild.20232701.d-22-00051. PubMed DOI PMC

Flouris AD, Spiropoulos Y, Sakellariou GJ, Koutedakis Y. Effect of seasonal programming on fetal development and longevity: Links with environmental temperature. Am. J. Hum. Biol. 2009;21(2):214–216. doi: 10.1002/ajhb.20818. PubMed DOI

Basu R, Sarovar V. Association between high ambient temperature and risk of stillbirth in California. Am. J. Epidemiol. 2016;183(10):894–901. doi: 10.1093/aje/kwv295. PubMed DOI

Rylander C, Odland JØ, Sandanger TM. Climate change and environmental impacts on maternal and newborn health with focus on Arctic populations. Glob. Health Action. 2011;4(1):8452. doi: 10.3402/gha.v4i0.8452. PubMed DOI PMC

Auger N, Naimi AI, Smargiassi A, Lo E, Kosatsky T. Extreme heat and risk of early delivery among preterm and term pregnancies. Epidemiology. 2014;25(3):344–350. doi: 10.1097/EDE.0000000000000074. PubMed DOI

Kuehn L, McCormick S. Heat exposure and maternal health in the face of climate change. Int. J. Environ. Res Public Health. 2017;14(8):853. doi: 10.3390/ijerph14080853. PubMed DOI PMC

Shashar S, Kloog I, Erez O, Shtein A, Yitshak-Sade M, Sarov B, Novack L. Temperature and preeclampsia: Epidemiological evidence that perturbation in maternal heat homeostasis affects pregnancy outcome. PLoS One. 2020;15(5):e0232877. doi: 10.1371/journal.pone.0232877. PubMed DOI PMC

Kasdorf E, Perlman JM. Hyperthermia, inflammation, and perinatal brain injury. Pediatr. Neurol. 2013;49(1):8–14. doi: 10.1016/j.pediatrneurol.2012.12.026. PubMed DOI

Asamoah B, Kjellstrom T, Östergren P-O. Is ambient heat exposure levels associated with miscarriage or stillbirths in hot regions? A cross-sectional study using survey data from the Ghana Maternal Health Survey 2007. Int. J. Biometeorol. 2018;62(3):319–330. doi: 10.1007/s00484-017-1402-5. PubMed DOI PMC

Rahman J, Fakhruddin S, Rahman AF, Halim M. Environmental heat stress among young working women: A pilot study. Ann Glob. Health. 2016;82(5):760–767. doi: 10.1016/j.aogh.2016.07.007. PubMed DOI

Vicedo-Cabrera AM, Olsson D, Forsberg B. Exposure to seasonal temperatures during the last month of gestation and the risk of preterm birth in Stockholm. Int. J. Environ. Res. Public Health. 2015;12(4):3962–3396. doi: 10.3390/ijerph120403962. PubMed DOI PMC

Rooney C, McMichael A, Kovats R, Coleman M. Excess mortality in England and Wales, and in Greater London, during the 1995 heat wave. J. Epidemiol. Commun. Health. 1998;52(8):482–486. doi: 10.1136/jech.52.8.482. PubMed DOI PMC

Kysely J, Kim J. Mortality during heat waves in South Korea, 1991 to 2005: How exceptional was the 1994 heat wave? Clim. Res. 2009;38:105–116. doi: 10.3354/cr00775. DOI

Basagña X, Sartini C, Barrera-Gómez J, Dadvand P, Cunillera J, Ostro B, Sunyer J, Medina-Ramón N. Heat waves and cause-specific mortality at all ages. Epidemiology. 2011;22(6):765–772. doi: 10.1097/EDE.0b013e31823031c5. PubMed DOI

Nitschke M, Tucker GR, Hansen AL, Williams S, Zhang Y, Bi P. Impact of two recent extreme heat episodes on morbidity and mortality in Adelaide, South Australia: A case series analysis. Environ. Health. 2011;42:1–10. doi: 10.1186/1476-069X-10-42. PubMed DOI PMC

Lawlor, D. A., Leon, D. A. & Smith, G. D. The association of ambient outdoor temperature throughout pregnancy and offspring birthweight: Findings from the Aberdeen Children of the 1950s cohort. BJOG112(5), 647–657 10.1111/j.1471-0528.2004.00488.x (2005). PubMed

Murray LJ, O’Reilly DP, Betts N, Patterson CC, Davey Smith G, Evans AE. Season and outdoor ambient temperature: Effects on birth weight. Obstet. Gynecol. 2000;96:689–695. doi: 10.1016/s0029-7844(00)01022-x. PubMed DOI

Cavalli-Sforza LL, Bodmer WF. The Genetics of Human Populations. Freeman; 1971.

Catalano R, Bruckner T, Smith KR. Ambient temperature predicts sex ratios and male longevity. PNAS. 2008;105(6):2244–2247. doi: 10.1073/pnas.0710711104. PubMed DOI PMC

Lerchl A. Sex ratios at birth and environmental temperatures. Naturwissenschaften. 1999;86:340–342. doi: 10.1007/s001140050630. PubMed DOI

McLachlan JC, Storey H. Hot male: Can sex in humans be modified by temperature? J. Theor. Biol. 2003;222(1):71–72. doi: 10.1016/s0022-5193(03)00014-6. PubMed DOI

Grech V, Savona-Ventura C, Vassallo-Agius P. Unexplained differences in sex ratios at birth in Europe and North America. BMJ. 2002;324:1010. doi: 10.1136/bmj.324.7344.1010. PubMed DOI PMC

Helle S, Helama S, Jokela J. Temperature-related birth sex ratio bias in historical Sami: Warm years bring more sons. Biol. Lett. 2008;4:60–62. doi: 10.1098/rsbl.2007.0482. PubMed DOI PMC

Murray, J. D., Deeming, D. C. & Ferguson, M. W. J. Size-dependent pigmentation-pattern formation in embryos of alligator mississippiensis: Time of initiation of pattern generation mechanism. Proc. R. Soc. B. Biol. Sci.239(1296), 279–293 http://www.jstor.org/stable/49461 (1990). PubMed

Grech V, Vassallo-Agius P, Savona-Ventura C. Declining male births with increasing geographical latitude in Europe. J. Epidemiol. Commun. Health. 2000;54(4):244–246. doi: 10.1136/jech.54.4.244. PubMed DOI PMC

Schmahl J, Capel B. Cell proliferation is necessary for the determination of male fate in the gonad. Dev. Biol. 2000;258(2):264–276. doi: 10.1016/S0012-1606(03)00122-2. PubMed DOI

Piprek RP, Kubiak JZ. Historia badań nad determinacją płci. Kosmos. 2019;68:523–533. doi: 10.36921/kos.2019_2516. DOI

McLaren, Z. & Wide, J. The Effect of Ambient Temperature during Pregnancy on Human Sex Ratios at Birth. https://paa.confex.com/paa/2017/mediafile/ExtendedAbstract/Paper16645/McLaren_Wilde_Temperature_Gender_9292016.pdf. Accessed 1 March 2024 (2016).

Hajdu T, Hajdu G. Temperature, climate change, and human conception rates: Evidence from Hungary. J. Popul. Econ. 2022;35(4):1751–1776. doi: 10.1007/s00148-020-00814-1. DOI

Rutledge JJ, Monson RL, Northey DL, Leibfried-Rutledge ML. Seasonality of cattle embryo production in a temperate region. Theriogenology. 1999;51:330. doi: 10.1016/S0093-691X(99)91889-7. DOI

De Rensis F, Scaramuzzi RJ. Heat stress and seasonal effects on reproduction in the dairy cow—A review. Theriogenology. 2003;60(6):1139–1151. doi: 10.1016/S0093-691X(03)00126-2. PubMed DOI

Wolfenson D, Roth Z, Meidan R. Impaired reproduction in heat-stressed cattle: Basic and applied aspects. Anim. Reprod. Sci. 2000;2(60–61):535–547. doi: 10.1016/s0378-4320(00)00102-0. PubMed DOI

Edwards MJ, Saunders RD, Shiota K. Effects of heat on embryos and foetuses. Int. J. Hyperthermia. 2003;19(3):295–324. doi: 10.1080/0265673021000039628. PubMed DOI

van Zutphen AR, Lin S, Fletcher BA, Hwang S-A. A population based case–control study of extreme summer temperature and birth defects. Environ. Health Perspect. 2012;120(10):1443–1449. doi: 10.1289/ehp.1104671. PubMed DOI PMC

Fukuda M, Fukuda K, Shimizu T, Møller H. Decline in sex ratio at birth after Kobe earthquake. Hum. Reprod. 1998;13(8):2321–2322. doi: 10.1093/humrep/13.8.2321. PubMed DOI

Fukuda M, Fukuda K, Shimizu T, Yomu-Ra W, Shimizu S. Kobe earthquake and reduced sperm motility. Hum. Reprod. 1996;11:1244–1246. doi: 10.1093/oxfordjournals.humrep.a019365. PubMed DOI

Gomendio M, Malo AF, Soler AJ, Fernández-Santos MR, Esteso MC, García AJ, Roldan ER, Garde J. Male fertility and sex ratio at birth in red deer. Science. 2006;314(5804):1445–1447. doi: 10.1126/science.1133064. PubMed DOI

Paul C, Murray AA, Spears N, Saunders PTK. A single, mild, transient scrotal heat stress causes DNA damage, subfertility and impairs formation of blastocysts in mice. Reproduction. 2008;136:73–84. doi: 10.1530/REP-08-0036. PubMed DOI

Yaeram J, Setchell BP, Maddocks S. Effect of heat stress on the fertility of male mice in vivo and in vitro. Reprod. Fertil. Dev. 2006;18:647–653. doi: 10.1071/RD05022. PubMed DOI

Brito LFC, Silva AEDF, Barbosa RT, Unanian MM, Kastelic JP. Effects of scrotal insulation on sperm production, semen quality, and testicular echotexture in Bos indicus and Bos indicus × Bos taurus bulls. Anim. Reprod. Sci. 2003;79:1–15. doi: 10.1016/S0378-4320(03)00082-4. PubMed DOI

Garcia-Oliveros LN, de Arruda RP, Batissaco L, Guilger Gonzaga VH, Moreira Nogueira VJ, Florez-Rodriguez SA, dos Santos Almeida F, Rodrigues Alves MB, Costa Pinto SC, Nichi M, de Agostini Losano JD, Vechiato Kawai GK, Carvalho Celeghini EC. Heat stress effects on bovine sperm cells: A chronological approach to early findings. Int. J. Biometeorol. 2020;64:1367–1378. doi: 10.1007/s00484-020-01917-w. PubMed DOI

Pérez-Crespo M, Pintado B, Gutiérrez-Adán A. Scrotal heat stress effects on sperm viability, sperm DNA integrity, and the offspring sex ratio in mice. Mol. Reprod. Dev. 2008;75:40–47. doi: 10.1002/mrd.20759. PubMed DOI

Boklage CE. Survival probability of human conceptions from fertilization to term. Int. J. Fertil. 1990;35(2):75, 79–80, 81–94. PubMed

Macklon NS, Geraedts JP, Fauser BC. Conception to ongoing pregnancy: The 'black box' of early pregnancy loss. Hum. Reprod. 2002;8(4):333–343. doi: 10.1093/humupd/8.4.333. PubMed DOI

Wilcox AJ, Weinberg CR, O’Connor JF, Baird DD, Schlatterer JP, Canfield RE, Armstrong EG, Nisula BC. Incidence of early loss of pregnancy. N. Engl. J. Med. 1988;319:189–194. doi: 10.1056/NEJM198807283190401. PubMed DOI

Trivers RL, Willard DE. Natural selection of parental ability to vary the sex ratio of offspring. Science. 1973;191(249–263):1973. doi: 10.1126/science.179.4068.90. PubMed DOI

Klimada 2.0. https://klimada2.ios.gov.pl/. Accessed 4 Mar 2024 (2024).

Kundzewicz, Z. W. Climate changes, their reasons and effects—Observations and projections. Landform Anal.15, 39–49. http://yadda.icm.edu.pl/baztech/element/bwmeta1.element.baztech-article-BUJ5-0052-0052. Accessed 4 Mar 2024 (2011).

Błażejczyk, K., Baranowski, J. & Błażejczyk, A. Wpływ Klimatu na Stan Zdrowia w Polsce: Stan Aktualny Oraz Prognoza do 2100 Roku (Wydawnictwo Akademickie SEDNO, 2015).

Grzeszczuk-Brendel, H. Miasto do Mieszkania. Zagadnienia Reformy Mieszkaniowej na Przełomie XIX i XX Wieku i jej Wprowadzenie w Poznaniu w Pierwszej Połowie XX Wieku (Wydawnictwo Politechniki Poznańskiej, 2012).

Trzeciakowski, L. Społeczeństwo, jego życie codzienne i kultura materialna. In Dzieje Poznania w Latach 1793–1945 (Topolski, J., Trzeciakowski, L. eds.). 296–320 (Wydawnictwo Naukowe PWN, 1994).

Die Gemeinden und Gutsbezirke des Preussischen Staates und ihre Bevölkerung. 4, Die Gemeinden und Gutsbezirke der Provinz Posen und ihre Bevölkerung: Nach den Urmaterialien der Allgemeinen Volkszählung vom 1. December 1871 (Verlag des Königlichen Statistischen Bureaus, 1874).

Łuczak, C. Życie Gospodarczo-Społeczne w Poznaniu 1815–1918 (Wydawnictwo Poznańskie, 1965).

Szulc, W. Położenie Klasy Robotniczej w Wielkopolsce w Latach 1871–1914 (Wydawnictwo Naukowe UAM, 1970).

Smosarski, W. Temperatura i Opady w Wielkopolsce (Ministerstwo Wyznań Religijnych i Oświecenia Publicznego, 1925).

Kolendowicz K, Czarnecki B, Półrolczak B, Taszarek M, Tomczyk AM, Szyga-Pluga K. Homogenization of air temperaturę and its long-term trends in Poznan (Poland) for the period 1848–2016. Theor. Appl. Climatol. 2019;136:1357–1370. doi: 10.1007/s00704-018-2560-z. DOI

Cunningham JM, Kim CY, Cristensen ER, Tester DJ, Parc Y, Burgart LJ, Halling KC, McDonnel SK, Schaid DJ, WalshVockley C, Kubly V, Nelson H, Michels VV, Thibodeau SN. The frequency of hereditary defective mismatch repair in a prospective series of unselected colorectal carcinomas. Am. J. Hum. Genet. 2001;69(5):1160. doi: 10.1086/323658. PubMed DOI PMC

Bhat RA, Kushtagi P. A re-look at the duration of human pregnancy. Singap. Med. J. 2006;12(47):1044–1048. PubMed

Hastie, T. J. & Tibshirani, R. J. Generalized Additive Models. 10.1201/9780203753781 (Boca Raton, 1990).

Wood, S. N. Generalized Additive Models: An Introduction with R. 2nd ed. 10.1201/9781315370279 (Boca Raton, 2017).

Wood SN, Pya N, Saefken B. Smoothing parameter and model selection for general smooth models (with discussion) J. Am. Stat. Asoc. 2016;111(516):1548–1575. doi: 10.1080/01621459.2016.1180986. DOI

Almon Sh. The distributed lag between capital appropriations and net expenditures. Econometrica. 1965;33:178–196. doi: 10.2307/1911894. DOI

Brabec M. Semiparametric Model for Short Term Effects of Air Pollution Upon Asthma Symptoms Exacerbations. Joint ISCB/ASC Meeting; 2018. pp. 26–30.

Judge GG, Griffiths WE, Hill RC, Lee T-C. The Theory and Practice of Econometrics. Wiley; 1980.

R Core Team. R: A Language and Environment for Statistical Computing. https://www.r-project.org/ (R Foundation for Statistical Computing, 2023).

Rocznik Demograficzny 2023 (Główny Urząd Statystyczny, 2023). https://stat.gov.pl/obszary-tematyczne/roczniki-statystyczne/roczniki-statystyczne/rocznik-demograficzny-2023,3,17.html. Accessed 16 June 2024 (2023).

Weng YH, Yang CY, Chiu YW. Neonatal outcomes in relation to sex differences: A national cohort survey in Taiwan. Biol. Sex Differ. 2015;6:30. doi: 10.1186/s13293-015-0052-8. PubMed DOI PMC

Bohn C, Vogel M, Poulain T, Spielau U, Hilbert C, Kiess W, Körner A. Birth weight increases with birth order despite decreasing maternal pregnancy weight gain. Acta Paediatr. 2021;110:1218–1224. doi: 10.1111/apa.15598. PubMed DOI

Chahnazarian A. Determinants of the sex ratio at birth: Review of recent literature. Soc. Biol. 1988;35(3–4):214–235. doi: 10.1080/19485565.1988.9988703. PubMed DOI

Liczbińska G, Sobkowiak A. Did the sex ratio at birth reflect social and economic inequalities? A pilot study of the Province of Poznań, 1875–1913. Poland's Demogr.Past (Przeszłość Demograficzna Polski) 2020;42:95–121. doi: 10.18276/pdp.2020.42-04. DOI

Ruckstuhl KE, Colijn GP, Amiot V, Vinish E. Mother's occupation and sex ratio at birth. BMC Pub. Health. 2010;10:269. doi: 10.1186/1471-2458-10-269. PubMed DOI PMC