Climate change could pose a significant risk to the reproductive health of Australians, according to a new large-scale study from Curtin University. The research reveals a potential link between extreme bioclimatic exposure during pregnancy and the birth weight of babies for their gestational age.
Researchers from the Curtin School of Population Health analyzed over 385,000 pregnancies in Western Australia from 2000 to 2015, covering the period from 12 weeks before conception to birth. The pregnancies included 9.8% and 9.9% of babies born either very small or large for their gestational age, respectively.
The team focused on the relationship between low and high birth weight for gestational age and an individual’s exposure to heat or cold (biothermal) stress during pregnancy.
To assess this, the researchers utilized the Universal Thermal Climate Index (UTCI), a modern composite biothermal tool that describes an individual’s physiological response to the thermal environment.
This study is the first to use the UTCI to measure bioclimatic exposure before and during pregnancy and the risks associated with being born very small or large for gestational age. It found that exposure to low and high biothermal stress during specific periods of pregnancy appeared to be associated with a higher risk of babies being either smaller or larger than expected for their gestational age at birth.
The average biothermal exposure ranged from 8.1 to 30.0 degrees Celsius, indicating mild cold stress and moderate heat stress on the UTCI scale. The study revealed that extreme biothermal exposures—1st percentile (cold stress) and 99th percentile (heat stress), compared to the median (no thermal stress)—were more closely linked to changes in birth weight for gestational age.
Lead researcher Dr. Sylvester Dodzi Nyadanu noted that this is especially true during certain stages of pregnancy. “The size of a baby at birth is closely linked to mortality risk during the first year, with developmental issues in childhood and a higher risk of various diseases in adulthood,” Dr. Nyadanu said.
“These findings support our concerns that the risk of having a baby who is very small or large for gestational age appears to increase with exposure to environmental conditions that cause biothermal stress in the later stages of pregnancy,” he added. “We also found that other subpopulations were at higher risk for abnormal fetal development due to exposure to biothermal stress, including non-Caucasians, male births, pregnancies in individuals aged 35 and older, those in rural areas, and those who smoked during pregnancy,” he emphasized.
Dr. Nyadanu stated that the study adds to the growing evidence of the threat posed by climate change to reproductive health, exacerbating heatwaves or cold spells, vector-borne diseases, natural disasters such as cyclones, floods, droughts, and fires, food and water insecurity, and the degradation of various physical and social environments that worsen existing health challenges. “Exposure to thermal stress increases dehydration and leads to oxidative stress and systemic inflammatory responses, resulting in adverse outcomes for reproductive health and fetal well-being,” he explained.
“Our research contributes to the increasing body of observational studies reporting maternal exposure to environmental temperatures and pregnancy outcomes, such as pregnancy complications, preterm birth, stillbirth, and low birth weight. Further studies are needed to determine which interventions will achieve better outcomes for parents and babies—especially among the specific vulnerable subpopulations identified in our study,” he emphasized. “Pregnancy is a vulnerable period for climate change, and thus any climate care intervention is reproductive health care,” he concluded.
