From melting ice caps to rising sea levels. You often hear about these things when the topic of climate change comes up. But the fact that a warmer world also affects the health of unborn children is not yet widely known. This was discovered by neonatologist and paediatrician Jasper Been (Erasmus MC). He observed that higher temperatures in the Netherlands increase the risk of premature births and low birth weight.
Been works as a paediatrician in the neonatal intensive care unit at Erasmus MC Sophia Children’s Hospital. There, he treats babies who are born far too early or who are seriously ill at birth. As well as providing patient care, he focuses on research into the causes of premature birth. 'Of course, the best thing would be if we didn’t need that care at all,' he says.
2.5 million pregnancies studied
The reason for the study stemmed from international research that had found a link between heat and pregnancy complications. But did that also apply to the Netherlands?
To answer that question, researchers analysed data from 2.5 million pregnancies over a period of fifteen years. This data was linked to temperature and humidity readings from KNMI weather stations. The analysis revealed that, in the Netherlands too, higher temperatures are associated with an increased risk of preterm birth and lower birth weight.
During the hot summer of 2023, it is estimated that around 500 additional premature births in the Netherlands were linked to the heat. Given a total of around 11,000 premature births per year, this is a substantial number.
Vulnerable groups are particularly at risk
What particularly struck the researchers was that the effects of heat are not evenly distributed. The risks appear to be greater for people in vulnerable circumstances, such as residents of deprived neighbourhoods or lower-income families.
This is likely due to a number of factors. People in these neighbourhoods are more likely to live in poorly insulated homes that heat up more quickly. These neighbourhoods also tend to have less green space, which means temperatures can rise higher than elsewhere in the city.
How does heat affect pregnancy?
It is not yet entirely clear exactly why heat leads to an increase in premature births. However, there are indications from previous research. For example, heat can reduce blood flow to the placenta, thereby restricting the baby’s growth. Heat also appears to make the uterus contract more easily, which can trigger premature birth.
The researchers found that the risks are already increasing on hot days, which are becoming increasingly common in the Netherlands. Particularly when hot weather persists for several days in a row, homes can heat up significantly. In poorly insulated houses, the temperature in bedrooms can then rise to well over 30 degree Celsius.
Rotterdam as a heat island
The research is particularly relevant for Rotterdam. Large cities retain heat for longer than their surrounding areas. This so-called heat island effect means that some neighbourhoods are significantly warmer than others.
Researchers are currently examining differences between neighbourhoods in Rotterdam. Previous analyses have already shown that pregnancy outcomes can vary significantly. For example, in some deprived neighbourhoods, approximately twice as many children are born with low birth weight as in nearby, more affluent neighbourhoods.
According to Been, that is an important point. ‘You’re actually already 1-0 down at birth, even though you had no say in the matter.’
More green spaces as a health measure
The findings have now led to discussions with Rotterdam City Council, housing associations and other stakeholders. More green spaces, better housing and extra care for pregnant women during hot spells are potential solutions.
Been points to the example of the Colombian city of MedellÃn, where large-scale greening has caused the temperature in parts of the city to drop by several degrees. According to him, this shows that climate measures are not only good for the environment but can also yield direct health benefits.
His message to policymakers is clear: continue with the greening of the city and the protection of people in the most vulnerable positions. Because health inequalities do not only arise at school or in the labour market, but often even before birth.
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Jasper Been was recently interviewed by the Dutch media outlets NOS and NRC about his research. The place where a child is born has a significant impact on their health around the time of birth.
More science stories? Have a look at our online magazine Erasmus Extra.
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