A woman’s exposure to high pollen levels in late pregnancy may increase the risk of early asthma in her child, according to Swedish researchers.
A number of studies have previously shown that there is an association with being born during a pollen season and an increased risk of allergies, according to the study authors from Umeå University.
Their study involved 110,000 pregnancies in the Stockholm area.
They found high levels of pollen exposure during the last 12 weeks of pregnancy resulted in a significantly increased risk of hospitalisation for asthma symptoms in the first year of life for a child.
The findings were adjusted to take into account factors such as maternal smoking and difference in pollen season.
The study authors said : “High levels of pollen exposure during late pregnancy were somewhat unexpectedly associated with an elevated risk of hospitalisation for asthma within the first year of life.”
They speculated that there may be several reasons for the association.
For example, they suggested high pollen exposure among pregnant women with pollen allergies could result in allergic reactions and asthma symptoms that may also affect the unborn child’s immune system development.
It is also possible that pregnant women with severe reactions to pollen suffer complications and sometimes give birth earlier than they otherwise would have done, which in itself increases the risk of respiratory problems in the child, they add.
“Further work is required to elucidate exactly how pollen exposure may prime the foetal immune system towards severe respiratory illness in early life,” the authors said.