Climate change will affect gender ratio among newborns, scientists say

Susan Scutti
By Susan Scutti, CNN
6 minute read
Updated 9:28 AM EST, Thu January 24, 2019
The nonprofit WaterAid asked pregnant women from around the world to share what they'll take to the hospital when they deliver their child. Some brought items that comfort them or clothes for the baby. Some had to bring their own basic medical supplies.<br /><br />Katy Shaw, 31, is originally from the United Kingdom and now lives in Melbourne, Australia. This will be her first baby.
The nonprofit WaterAid asked pregnant women from around the world to share what they'll take to the hospital when they deliver their child. Some brought items that comfort them or clothes for the baby. Some had to bring their own basic medical supplies.

Katy Shaw, 31, is originally from the United Kingdom and now lives in Melbourne, Australia. This will be her first baby.
James Grant Photography 2014/James Grant/Wateraid
Katy Shaw's maternity bag.
Katy Shaw's maternity bag.
James Grant/Wateraid
Katy Shaw's bag includes: toiletries, snacks, diapers, hat, socks, mittens, clothes and swaddles for the baby, clothes for the mom, nightgowns, maternity underwear, maternity pads, nursing pads and massage oils.
Katy Shaw's bag includes: toiletries, snacks, diapers, hat, socks, mittens, clothes and swaddles for the baby, clothes for the mom, nightgowns, maternity underwear, maternity pads, nursing pads and massage oils.
James Grant/Wateriad
Agnes Noti, 22, of Tanzania, was photographed at the Kiomboi District Hospital as she was prepared to give birth to her third child. There was no source of water in the rooms where mothers deliver babies or care for newborns. There was one toilet and women had access to a sink that's also used to wash medical equipment. The water they drink is purchased from a shop, she said.
Agnes Noti, 22, of Tanzania, was photographed at the Kiomboi District Hospital as she was prepared to give birth to her third child. There was no source of water in the rooms where mothers deliver babies or care for newborns. There was one toilet and women had access to a sink that's also used to wash medical equipment. The water they drink is purchased from a shop, she said.
Anna Kari/WaterAid
Agnes Noti's bag includes: clothes for the baby, a blanket for the baby, socks, a basin, a flask and tea.
Agnes Noti's bag includes: clothes for the baby, a blanket for the baby, socks, a basin, a flask and tea.
Anna Kari/Wateraid
Ellen Phiri, 23, of Malawi, was photographed as she prepared to give birth at the Simulemba Health Centre. It has no clean running water, no sterilization equipment and four toilets for 400 people, according to WaterAid. Water is collected from a water pump shared with the community.
Ellen Phiri, 23, of Malawi, was photographed as she prepared to give birth at the Simulemba Health Centre. It has no clean running water, no sterilization equipment and four toilets for 400 people, according to WaterAid. Water is collected from a water pump shared with the community.
Jenny Lewis/Wateraid
Ellen Phiri's bag includes: a flashlight because there is no electricity, a black plastic sheet to cover the delivery bed because it is it hard to clean the area, a razor blade to cut the umbilical cord, string to tie the umbilical cord, 200 Malawian Kwacha for food, three large sarongs for the mother to wear and to wrap her baby in.
Ellen Phiri's bag includes: a flashlight because there is no electricity, a black plastic sheet to cover the delivery bed because it is it hard to clean the area, a razor blade to cut the umbilical cord, string to tie the umbilical cord, 200 Malawian Kwacha for food, three large sarongs for the mother to wear and to wrap her baby in.
Jenny Lewis
Hazel Shandumba, 27, is from Zambia. There is no running water in the maternity ward where she planned to give birth.
Hazel Shandumba, 27, is from Zambia. There is no running water in the maternity ward where she planned to give birth.
Chileshe Chanda/Wateraid
Hazel Shandumba's maternity bag.
Hazel Shandumba's maternity bag.
Chileshe Chanda/Wateraid
Hazel Shandumba's birth bag includes: baby blanket, cotton wool, a sarong, clothes for the baby, napkins, a basin for water, and a roll of plastic to put on the bed because it is difficult to keep the area clean.
Hazel Shandumba's birth bag includes: baby blanket, cotton wool, a sarong, clothes for the baby, napkins, a basin for water, and a roll of plastic to put on the bed because it is difficult to keep the area clean.
Chileshe Chanda/Wateraid
Razafindrabary Claudine, 26, was photographed in Madagascar. She said there's running water near her home in her village, so she doesn't have to walk far to fetch water.
Razafindrabary Claudine, 26, was photographed in Madagascar. She said there's running water near her home in her village, so she doesn't have to walk far to fetch water.
Ernest Randriarimalala/WaterAid
Razafindrabary Claudine's maternity basket.
Razafindrabary Claudine's maternity basket.
Ernest Randriarimalala/WaterAid
Razafindrabary Claudine's birth basket includes: Clothes for the baby, cotton wool, alcohol for cleaning, diapers, a flask, a bucket and sanitary pads.
Razafindrabary Claudine's birth basket includes: Clothes for the baby, cotton wool, alcohol for cleaning, diapers, a flask, a bucket and sanitary pads.
Ernest Randriarimalala/WaterAid
Deanna Neiers lives in New York and was photographed at home before giving birth to her first baby. <br />"I feel so happy nurturing this life inside of me, it truly is a miracle," she said. "I also am very fortunate to live within walking distance of one of the best hospitals in New York City. Being pregnant certainly heightens your awareness of how fortunate we are to have access to great birthing facilities and clean water."
Deanna Neiers lives in New York and was photographed at home before giving birth to her first baby.
"I feel so happy nurturing this life inside of me, it truly is a miracle," she said. "I also am very fortunate to live within walking distance of one of the best hospitals in New York City. Being pregnant certainly heightens your awareness of how fortunate we are to have access to great birthing facilities and clean water."
John Neiers/Wateraid
Deanna Neiers' maternity bag.
Deanna Neiers' maternity bag.
Deanna Neiers/Wateraid
Deanna Neiers maternity bag includes: Music player, coconut oil for massage, lavender oil, arnica gel, snacks, nursing bra and pads, nursing pillow, comfortable clothes to wear at the hospital and on her return home, soft swaddle blanket for the baby, clothes for the baby and a hat for the baby.
Deanna Neiers maternity bag includes: Music player, coconut oil for massage, lavender oil, arnica gel, snacks, nursing bra and pads, nursing pillow, comfortable clothes to wear at the hospital and on her return home, soft swaddle blanket for the baby, clothes for the baby and a hat for the baby.
Deanna Neiers/Wateraid
Joanna Laurie, 34, lives in London, and is expecting her first baby."The most important thing in the bag is the blanket my mum gave me to bring the baby home in, the same one my mother brought me home in," she said.
Joanna Laurie, 34, lives in London, and is expecting her first baby."The most important thing in the bag is the blanket my mum gave me to bring the baby home in, the same one my mother brought me home in," she said.
Anna Karl/Wateraid
Joanna Laurie's birth bag.
Joanna Laurie's birth bag.
Anna Karl/Wateraid
Joanna Laurie's bag includes: diapers, clothes for the baby, clothes for mom, snacks, towel for mom, toiletries, maternity pads, iPad, water bottle, medical notes, a blanket and a maternity TENS machine for pain.
Joanna Laurie's bag includes: diapers, clothes for the baby, clothes for mom, snacks, towel for mom, toiletries, maternity pads, iPad, water bottle, medical notes, a blanket and a maternity TENS machine for pain.
Anna Karl/Wateraid
Birth bags from around the world
CNN  — 

Global warming will have a variety of effects on our planet, yet it may also directly impact our human biology, research suggests.

Specifically, climate change could alter the proportion of male and female newborns, with more boys born in places where temperatures rise and fewer boys born in places with other environmental changes, such as drought or wildfire caused by global warming.

A recent study in Japan found a link between temperature fluctuations and a lower male-to-female sex ratio at birth, with conceptions of boys especially vulnerable to external stress factors, wrote Dr. Misao Fukuda, lead study author and founder of the M&K Health Institute in Hyogo.

03 wildlife poy 2018
Cristobal Serrano/Natural History Museum

Climate change: Do you know the basics?

Last summer, Fukuda and his colleagues published a separate study looking at births in areas hit by environmental events that caused extreme stress. They included Hyogo Prefecture after the Kobe earthquake of 1995; Tohoku after the Great East Japan Earthquake of 2011 (and subsequent nuclear disaster at the Fukushima Daichii power plant); and Kumamoto Prefecture after the 2016 earthquakes.