Link between air pollution and low birth weight in twins

Doctoral research conducted by Esmée Bijnens (Hasselt University/Maastricht University) found that the more exposure to air pollution during pregnancy, the higher the chance of low birth weight in twins. These results, based on data from the Oost-Vlaams Meerlingenregister (East Flemish twins registry), reveal that good air quality and green urban planning have positive health effects at birth and later in life.

The effects of air pollution on the health of adults has been investigated in previous studies, but there is limited knowledge about how environmental factors influence the earlier stages of life. A research team from the universities of Hasselt and Maastricht investigated how air pollution, traffic pollution and access to green areas during pregnancy influenced birth weight and age biomarkers in placental tissue. This studied focused primarily on twins. ‘Studying twins allows us to distinguish between the relative importance of genes and the environment on these biomarkers,’ explains Dr Esmée Bijnens.

Risk factors
The study, which included 4,760 twins, found that air pollution formed an important risk factor. ‘The more exposure to air pollution during pregnancy, the higher the risk of low birth weight in twins, in proportion to the duration of the pregnancy,’ explains Bijnens. ‘We found that an increase in air pollution of 10 micrograms per cubic metre led to a 34% increase in the number of children with low birth weight.’

These results demonstrate that good air quality and good urban planning with sufficient green areas have a beneficial effect on the health of newborns. If, in the future, we manage to stay under the air quality threshold set by the World Health Organization (20 micrograms per cubic metre), the risk of low birth weight would decrease by 40% in twins born between weeks 32 and 36 of pregnancy.

Traffic pollution
To study the effects of traffic pollution around the mother's home, the researchers examined telomere length in placental tissue in a small group of twins. ‘Telomeres are located at the ends of chromosomes and protect the genetic material. They help us determine biological age and the aging process: the older we get, the shorter these telomeres become,’ says Bijnens.

The researchers measured the telomeres at birth and later in life and found a link between living in a high-traffic area and short telomeres in the placenta and later in life. To illustrate: doubling the distance between the home and the nearest road would shorten placental telomeres by 5.3%, thereby slowing the aging process.

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