‘Rising temperatures could increase number of children born with heart defects, infertility’

Global warming could mean more children are born with potentially deadly heart defects.

Being exposed to unusually high temperatures during pregnancy increases the chance of damage to the internal organs, scientists say.

Research predicts there could be 7,000 extra cases of heart defects between 2025 and 2035 in eight United States (US) states with a combined population of approximately 110 million people.

Scaled up to the global population, this suggests climate change could contribute to around 40,000 congenital heart defects per year.

Researchers at the University of Albany in New York made their predictions using forecasts of the number of births and heat increases over the 11-year period.

They used data from the US states of Arkansas, Iowa, Texas, California, New York, North Carolina, Utah and Georgia.

They aren’t sure exactly why increased heat makes a baby more likely to have heart problems.

But animal studies suggest exposing a foetus to temperatures outside the mother’s normal experience may trigger cell death or damage proteins used in development.

To make their predictions, the New York scientists considered the number of excessively hot days during a woman’s pregnancy, the frequency of heat waves lasting three days or more, and the length of heat waves.

“It would be prudent for women in the early weeks of pregnancy to avoid heat extremes,” said Dr Shao Lin, director of environmental health sciences at Albany.

Dr. Wangjian Zhang, the study’s lead author, added: “Our results highlight the dramatic ways in which climate change can affect human health.

“And [they] suggest that pediatric heart disease stemming from structural heart malformations may become an important consequence of rising temperatures.”

The study was published in JAHA: The Journal of the American Heart Association.

The research comes after health experts this month warned global warming will kill far more people than the World Health Organization predicts.

Congenital heart defects are development problems which happen while a baby is in the womb and stop the heart from working properly.

Defects include holes in the heart, narrowing of the largest arteries, constricted valves, or an underdeveloped heart.

Signs a baby could have congenital heart disease include a rapid heartbeat, rapid breathing, swelling of the legs or stomach, and extreme tiredness and fatigue.
lves and the arteries they’re connected to have swapped positions.

Sir Andrew Haines, from the London School of Hygiene and Tropical Medicines, and the University of Washington’s Professor Kristie Ebi gave their warning in the New England Journal of Medicine.

They said the WHO’s estimate of 250,000 extra deaths per year because of soaring temperatures was too ‘conservative’.

As well as deaths from heat stress and malaria caused by burgeoning mosquito populations, there are other factors the WHO didn’t take into account, they said.

Extreme poverty, lung conditions caused by worse air quality, reduced access to clean water, smaller farm yields, and violence triggered by migration will all add to the deaths, Sir Andrew and Professor Ebi warned.

Also, rising temperatures could make some species sterile and see them succumb to the effects of climate change earlier than currently thought, scientists at the University of Liverpool, United Kingdom (U.K.) warn.

“There is a risk that we are underestimating the impact of climate change on species survival because we have focused on the temperatures that are lethal to organisms, rather than the temperatures at which organisms can no longer breed,” explains evolutionary biologist Dr. Tom Price from the University’s Institute of Integrative Biology.

Currently, biologists and conservationists are trying to predict where species will be lost due to climate change, so they can build suitable reserves in the locations they will eventually need to move to. However, most of the data on when temperature will prevent species surviving in an area is based on the ‘critical thermal limit’ or CTL – the temperature at which they collapse, stop moving or die.

In a new opinion article published in Trends in Ecology and Evolution, the researchers highlight that extensive data from a wide variety of plants and animals suggests that organisms lose fertility at lower temperatures than their CTL.

Certain groups are thought to be most vulnerable to climate-induced fertility loss, including cold-blooded animals and aquatic species. “Currently the information we have suggests this will be a serious issue for many organisms. But which ones are most at risk? Are fertility losses going to be enough to wipe out populations, or can just a few fertile individuals keep populations going? At the moment, we just don’t know. We need more data,” says Price.

To help address this, the researchers propose another measure of how organisms function at extreme temperatures that focuses on fertility, which they have called the Thermal Fertility Limit or ‘TFL’.

“We think that if biologists study TFLs as well as CTLs then we will be able to work out whether fertility losses due to climate change are something to worry about, which organisms are particularly vulnerable to these thermal fertility losses, and how to design conservation programmes that will allow species to survive our changing climate.

“We need researchers across the world, working in very different systems, from fish, to coral, to flowers, to mammals and flies, to find a way to measure how temperature impacts fertility in that organism and compare it to estimates of the temperature at which they die or stop functioning,” urges Dr Price.

The work was carried out in collaboration with scientists from the University of Leeds, University of Melbourne and Stockholm University and was funded by the UK Natural Environment Research Council (NERC).

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