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Heat during pregnancy causes biological ageing in newborns    6 nov 2019

Heat during pregnancy causes biological ageing in newborns
6 nov 2019


Prof. dr. Tim NAWROT



Exposure to higher temperatures during pregnancy can lead to biological ageing in infants. ‘In our research at Hasselt University we’ve discovered that heat reduces the length of newborn children’s telomeres,’ says Dr Dries Martens. ‘Telomeres are the ends of our chromosomes, and their length determines the lifespan of our cells. Shorter telomeres potentially indicate a lower life expectancy.’

‘An earlier American study1 had already shown that temperature during pregnancy can be linked to the life expectancy of the newborn child,’ says Prof. Tim Nawrot. ‘But a biological explanation for this had never been found before. We’ve now found a connection between heat and the length of telomeres at birth, with which we can now solve part of this puzzle.’ The results of this research are being published in the scientific journal Environmental Health Perspectives. 

1.100 newborns evaluated

‘For our study, we evaluated telomere length in 1,100 newborns from the Belgian ENVIRONAGE birth cohort. In cord blood we could see that telomere length varied in the infants, and that exposure to heat played a clear role in this,’ explains Dries Martens.  ‘Specifically, we observed that the length of the telomeres was on the average 1.5 percent shorter for every degree that the weekly temperature during pregnancy rose above 19.5 degrees Celsius. That could amount to telomeres that were more than 3 percent shorter in the final weeks of pregnancy.’

How serious is this for children? ‘We want to stress that the picture is complex,’ say the researchers. ‘It’s not the case that children whose mothers were pregnant during a heat wave are less healthy. Other factors during the rest of your life, such as air pollution, smoking and lifestyle, have a further impact on our telomeres. However, we know that later in life, shorter telomeres are linked to a higher risk of cardiovascular disease. That makes these results striking, because it shows that not all newborns are at the same biological age, and that exposure to heat during pregnancy plays a role in this,’ says Dr Dries Martens.

Climate change

‘What’s clear is that as we start experiencing more periods of warmer weather as a result of climate change, this is an important finding to take into account,’ says Prof. Tim Nawrot. ‘Climate change brings new health risks to humans. For certain effects adaptation to higher temperatures may occur over generations, but we don’t know how fast that will happen. It’s therefore advisable for pregnant women not to over-expose themselves to excessive temperatures  – especially as we, and others, have already demonstrated in earlier research at Hasselt University that heat during pregnancy can also lead to an increase in the number of premature births².’

So it’s best to avoid exposure to temperatures that are too high, but what those temperatures are, depends on the climate that people are used to, the researchers say. ‘Every population is adapted to a specific climate: we can see that, for example, from the fact that extreme heat or cold raises mortality rates, whereas on days with an average, normal temperature the mortality rate is at its lowest. In southern Europe, the normal temperature is higher than in Belgium, while in Scandinavian countries it’s lower. Our study now shows that ambient temperature not only plays a role in terms of mortality later in life, but also influences biological ageing processes, starting even before birth.’ 

This research received financial support from FWO and ERC.

You can find the complete study in Environmental Health Perspectives HERE.

1: Catalano et al., 2008, PNAS

²: Cox et al. J Epidemiol Community Health 2016

More information:

Prof. dr. Tim Nawrot: 0032 490 / 57 70 13 tim.nawrot@uhasselt.be