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The male to female ratio of newborn infants in Japan in relation to climate change, earthquakes, fetal deaths, and singleton male and female birth weights
Early Human Development xxx (xxxx) xxxx
Contents lists available at ScienceDirect
Early Human Development journal homepage: www.elsevier.com/locate/earlhumdev
The male to female ratio of newborn infants in Japan in relation to climate change, earthquakes, fetal deaths, and singleton male and female birth weights ABSTRACT
We have updated our work regarding climate extremes in Japan and the consequences of the huge earthquake in the Fukushima Prefecture in year 2011. We have interchangeably used the term sex ratio at birth, sex ratio of births. This ratio describes the secondary sex ratio, whereas the primary sex ratio designates the male/ female ratio at fertilization. The underlying mechanisms of declines in sex ratios at birth may be related to decreased fertilization of XY embryos by reduced motility of Y spermatozoa from male factor approach and increased cortisol secretion prior to conception from a female factor approach. We have shown that the declines in sex ratio at birth were observed 9 months after the Kobe earthquake but 10 months after the Tohoku and Kumamoto earthquakes. The temperature difference may be associated positively with sex ratio of fetal deaths and negatively with sex ratio of births and with singleton male and female birth weights.
We have updated work previously published by our group [1] including more information on the subject and new data on sex ratios of fetal deaths and newborn infants during different stress conditions. We have also included climate extremes in Japan and the consequences of the huge earthquake in the Fukushima Prefecture in year 2011. We have also expanded our previous results based upon all the confirmed data and produced two additional graphs. In this text we have used the male to female ratio of children at birth as the sex ratio. This ratio describes the secondary sex ratio, whereas the primary sex ratio designates the male/female ratio at fertilization. We have interchangeably used the term sex ratio at birth, sex ratio of births, birth sex ratio, sex ratio of newborn infants, male to female ratio of newborns and offspring sex ratio as an expression of the secondary sex ratio. We have tested a possible association between mean temperature differences and male to female ratios of spontaneous fetal deaths after 12 weeks of gestation and male to female ratios of births from 1968 to 2012 in Japan in two different ways: i) As a long-term effect of climate warming on male to female ratios of fetal deaths and newborn infants we found a significant positive association between yearly mean temperature differences and sex ratios of fetal deaths, while we found a significant negative association between temperature differences and sex ratios of births. The
https://doi.org/10.1016/j.earlhumdev.2019.104861
0378-3782/ © 2019 Published by Elsevier B.V.
sex ratios of fetal deaths have been increasing steadily along with temperature differences, whereas the sex ratios of newborn infants have been decreasing since the 1970s. ii) As a short-term effect of climate change on fetal death rates and sex ratios of births we found two climate extremes, the hottest summer in 2010 and the coldest January in 2011 prior to the Tohoku earthquake (March 11, 2011), which showed significant increases of spontaneous fetal death rate immediately and significant declines of sex ratio at birth nine months later. The Tohoku earthquake indicated local effects in Miyagi Prefecture but did not indicate nationwide effects on the sex ratio of births in all Japan. Particularly cold winters occurred before 1990 while particular warm summers seemed to occur more frequently after 1990. The underlying mechanisms of declines in sex ratios at birth may be related to decreased fertilization of XY embryos by reduced motility of Y spermatozoa from male factor approach and increased cortisol secretion prior to conception, low level of glucose at implantation and/or increased maternal adrenal androgens during pregnancy from a female factor approach. The present data suggest that the recent temperature fluctuation in Japan appears to be linked to a lower male to female ratio of newborn infants partially via increased male fetal deaths. Like sea turtles human male concepti appear to be especially vulnerable to external stress factors including climate
Early Human Development xxx (xxxx) xxxx
Fig. 1. Yearly mean temperature differences (°C: the sum of monthly mean temperature minus the mean temperature during the previous 30 years for the same month/12) and male: female ratios of fetal deaths after 12 weeks of gestation and births from 1968 to 2012 in Japan.
changes. In order not to share the same fate as the sea turtle, with 90% females, temperature differences and male to female ratios of fetal deaths and newborn infants are of great importance to human reproductive health and balance between the sexes. We must take every caution to monitor these indicators for future human reproductive health [2].
Tohoku earthquake and Kumamoto earthquakes. We have published the figure showing yearly temperature differences and male: female ratios of fetal deaths after 12 weeks of gestation and births from 1968 to 2012 in Japan (Fig. 1) [1,2]. Following this figure we added 5 years until 2017 and singleton male and female birth weights into the previous figure. The temperature difference may be associated positively with sex ratio of fetal deaths and negatively with sex ratio of births and with singleton male and female birth weights (Fig. 2) [5].
We have previously published work on the Kobe [3] and Tohoku earthquakes [1]. Following these works we added Kumamoto earthquake [4]. We have shown that the declines in sex ratio at birth were observed 9 months after the Kobe earthquake but 10 months after the
2
Early Human Development xxx (xxxx) xxxx
Fig. 2. Yearly mean temperature differences (°C: the sum of monthly mean temperature minus the mean temperature during the previous 30 years for the same month/12), male: female ratio of spontaneous fetal deaths after 12 weeks gestation, male: female ratio of births and singleton male and female mean birth weights (kg) from 1968 to 2017 in Japan.
References
[4] M. Fukuda, K. Fukuda, S. Mason, T. Shimizu, C. Yding Andersen, The sex ratio at birth after recent major earthquakes in Japan, Early Hum. Dev. 123 (2018) 30–31. [5] M. Fukuda, K. Fukuda, S. Mason, T. Shimizu, C. Yding Andersen, Are fetal mortality and a trend towards reduced birth weight of infants associated with climate changes in Japan? Early Hum. Dev. 132 (2019) 37–38.
[1] M. Fukuda, K. Fukuda, T. Shimizu, M. Nobunaga, L.S. Mamsen, C. Yding Andersen, Climate change is associated with male to female ratios of fetal deaths and newborn infants in Japan, Fertil. Steril. 102 (2014) 1364–1370. [2] M. Fukuda, T. Shimizu, C. Yding Andersen, Climate Change, Tohoku Earthquake and Sex Ratio of Fetal Death & Birth. The Male to Female Ratio of Newborn Infants in Japan in Relation to Climate Change, Tohoku Earthquake and Fetal Deaths, Lap Lambert Academic Publishing, Saarbrücken, Germany, 2015, pp. 1–81. [3] M. Fukuda, K. Fukuda, T. Shimizu, H. Møller, Decline in sex ratio at birth after Kobe earthquake, Hum. Reprod. 13 (1998) 2321–2322.
⁎
Misao Fukuda , Kiyomi Fukuda, M&K Health Institute, 30-9 Kariya, Ako, Hyogo 678-0239, Japan E-mail address: [email protected] (M. Fukuda). ⁎
Corresponding author. 3
Contents lists available at ScienceDirect
Early Human Development journal homepage: www.elsevier.com/locate/earlhumdev
The male to female ratio of newborn infants in Japan in relation to climate change, earthquakes, fetal deaths, and singleton male and female birth weights ABSTRACT
We have updated our work regarding climate extremes in Japan and the consequences of the huge earthquake in the Fukushima Prefecture in year 2011. We have interchangeably used the term sex ratio at birth, sex ratio of births. This ratio describes the secondary sex ratio, whereas the primary sex ratio designates the male/ female ratio at fertilization. The underlying mechanisms of declines in sex ratios at birth may be related to decreased fertilization of XY embryos by reduced motility of Y spermatozoa from male factor approach and increased cortisol secretion prior to conception from a female factor approach. We have shown that the declines in sex ratio at birth were observed 9 months after the Kobe earthquake but 10 months after the Tohoku and Kumamoto earthquakes. The temperature difference may be associated positively with sex ratio of fetal deaths and negatively with sex ratio of births and with singleton male and female birth weights.
We have updated work previously published by our group [1] including more information on the subject and new data on sex ratios of fetal deaths and newborn infants during different stress conditions. We have also included climate extremes in Japan and the consequences of the huge earthquake in the Fukushima Prefecture in year 2011. We have also expanded our previous results based upon all the confirmed data and produced two additional graphs. In this text we have used the male to female ratio of children at birth as the sex ratio. This ratio describes the secondary sex ratio, whereas the primary sex ratio designates the male/female ratio at fertilization. We have interchangeably used the term sex ratio at birth, sex ratio of births, birth sex ratio, sex ratio of newborn infants, male to female ratio of newborns and offspring sex ratio as an expression of the secondary sex ratio. We have tested a possible association between mean temperature differences and male to female ratios of spontaneous fetal deaths after 12 weeks of gestation and male to female ratios of births from 1968 to 2012 in Japan in two different ways: i) As a long-term effect of climate warming on male to female ratios of fetal deaths and newborn infants we found a significant positive association between yearly mean temperature differences and sex ratios of fetal deaths, while we found a significant negative association between temperature differences and sex ratios of births. The
https://doi.org/10.1016/j.earlhumdev.2019.104861
0378-3782/ © 2019 Published by Elsevier B.V.
sex ratios of fetal deaths have been increasing steadily along with temperature differences, whereas the sex ratios of newborn infants have been decreasing since the 1970s. ii) As a short-term effect of climate change on fetal death rates and sex ratios of births we found two climate extremes, the hottest summer in 2010 and the coldest January in 2011 prior to the Tohoku earthquake (March 11, 2011), which showed significant increases of spontaneous fetal death rate immediately and significant declines of sex ratio at birth nine months later. The Tohoku earthquake indicated local effects in Miyagi Prefecture but did not indicate nationwide effects on the sex ratio of births in all Japan. Particularly cold winters occurred before 1990 while particular warm summers seemed to occur more frequently after 1990. The underlying mechanisms of declines in sex ratios at birth may be related to decreased fertilization of XY embryos by reduced motility of Y spermatozoa from male factor approach and increased cortisol secretion prior to conception, low level of glucose at implantation and/or increased maternal adrenal androgens during pregnancy from a female factor approach. The present data suggest that the recent temperature fluctuation in Japan appears to be linked to a lower male to female ratio of newborn infants partially via increased male fetal deaths. Like sea turtles human male concepti appear to be especially vulnerable to external stress factors including climate
Early Human Development xxx (xxxx) xxxx
Fig. 1. Yearly mean temperature differences (°C: the sum of monthly mean temperature minus the mean temperature during the previous 30 years for the same month/12) and male: female ratios of fetal deaths after 12 weeks of gestation and births from 1968 to 2012 in Japan.
changes. In order not to share the same fate as the sea turtle, with 90% females, temperature differences and male to female ratios of fetal deaths and newborn infants are of great importance to human reproductive health and balance between the sexes. We must take every caution to monitor these indicators for future human reproductive health [2].
Tohoku earthquake and Kumamoto earthquakes. We have published the figure showing yearly temperature differences and male: female ratios of fetal deaths after 12 weeks of gestation and births from 1968 to 2012 in Japan (Fig. 1) [1,2]. Following this figure we added 5 years until 2017 and singleton male and female birth weights into the previous figure. The temperature difference may be associated positively with sex ratio of fetal deaths and negatively with sex ratio of births and with singleton male and female birth weights (Fig. 2) [5].
We have previously published work on the Kobe [3] and Tohoku earthquakes [1]. Following these works we added Kumamoto earthquake [4]. We have shown that the declines in sex ratio at birth were observed 9 months after the Kobe earthquake but 10 months after the
2
Early Human Development xxx (xxxx) xxxx
Fig. 2. Yearly mean temperature differences (°C: the sum of monthly mean temperature minus the mean temperature during the previous 30 years for the same month/12), male: female ratio of spontaneous fetal deaths after 12 weeks gestation, male: female ratio of births and singleton male and female mean birth weights (kg) from 1968 to 2017 in Japan.
References
[4] M. Fukuda, K. Fukuda, S. Mason, T. Shimizu, C. Yding Andersen, The sex ratio at birth after recent major earthquakes in Japan, Early Hum. Dev. 123 (2018) 30–31. [5] M. Fukuda, K. Fukuda, S. Mason, T. Shimizu, C. Yding Andersen, Are fetal mortality and a trend towards reduced birth weight of infants associated with climate changes in Japan? Early Hum. Dev. 132 (2019) 37–38.
[1] M. Fukuda, K. Fukuda, T. Shimizu, M. Nobunaga, L.S. Mamsen, C. Yding Andersen, Climate change is associated with male to female ratios of fetal deaths and newborn infants in Japan, Fertil. Steril. 102 (2014) 1364–1370. [2] M. Fukuda, T. Shimizu, C. Yding Andersen, Climate Change, Tohoku Earthquake and Sex Ratio of Fetal Death & Birth. The Male to Female Ratio of Newborn Infants in Japan in Relation to Climate Change, Tohoku Earthquake and Fetal Deaths, Lap Lambert Academic Publishing, Saarbrücken, Germany, 2015, pp. 1–81. [3] M. Fukuda, K. Fukuda, T. Shimizu, H. Møller, Decline in sex ratio at birth after Kobe earthquake, Hum. Reprod. 13 (1998) 2321–2322.
⁎
Misao Fukuda , Kiyomi Fukuda, M&K Health Institute, 30-9 Kariya, Ako, Hyogo 678-0239, Japan E-mail address: [email protected] (M. Fukuda). ⁎
Corresponding author. 3