Climate change could be impacting babies' birth weights

Researchers at the Curtin School of Population Health say global warming could pose a big risk to Australians' reproductive health.

A study examined more than 385,000 pregnancies in Western Australia between 2000 and 2015, from 12 weeks before conception until birth.

The results showed that both extreme cold and heat exposures during the latter stages of pregnancy caused both small and large baby sizes, but the effects were greater for cold than heat exposure.

Environmental and population health researcher Sylvester Dodzi Nyadanu said the findings were part of the growing evidence of the threat climate change posed to reproductive health.

This includes when mothers are exposed to extreme weather during pregnancy, such as heatwaves, floods, droughts, cyclones and bushfires.

These can lead to increased disease transmission in the community, food and water insecurity, and disruption to social environments.

"Thermal stress exposures increase dehydration and induce oxidative stress and systemic inflammatory responses, leading to adverse reproductive and foetal health outcomes," he said on Monday.

The study also found some sub-populations were at higher risk of abnormal foetal growth due to exposure to biothermal stress, including non-Caucasian people.

Pregnancies when mothers were aged 35 and over, smoked or lived in rural areas, along with those women carrying a baby boy were also at greater risk.

The research adds to the growing collection of observational studies reporting on maternal exposure to ambient temperature and pregnancy outcomes such as pregnancy complications, preterm birth, stillbirth and low birth weight.

"There needs to be further studies into what interventions will achieve better results for parents and babies - especially in the specific vulnerable sub-populations identified in our study," Dr Nyadanu said.

The study was published in the journal Environmental Health Perspectives.

Australian Associated Press