New York, Oct 30 (IANS): Exposure to air pollution during pregnancy is associated with reduced cardiac response to stress in their six-month-old infants, warns a new study.

Decreased heart rate variability, as observed in this study, is a known risk factor for mental and physical health problems in later life.

Variability in how the heart rate responds to stressful experiences is essential for maintaining optimal functioning of the cardiovascular, respiratory, and digestive systems and also is central to emotional well-being and resilience to stress over one's lifetime.

Air pollution's negative effect on heart rate variability has previously been found to lead to medical and psychological conditions such as heart disease, asthma, allergies, and mood or behavioural disorders in studies of older children, adolescents, and adults.

"These findings, in combination with increasing worldwide exposure to particulate air pollution, highlight the importance of examining early-life exposure to air pollution in relation to negative medical, developmental, and psychological outcomes," said senior author Rosalind Wright from Icahn School of Medicine at Mount Sinai in New York.

For the study, the researchers studied 237 Boston-based mothers and their infants and used satellite data and air pollution monitors to determine the level of particulate air pollution the mothers were exposed to during pregnancy.

The air pollution levels in this study were similar to levels experienced by the general US population.

By studying the babies' heart rate and respiration at age six months, the researchers found that the higher the level of the mother's exposure to air pollution in pregnancy, the less variability in the infant's heart rate in response to a stress challenge.

The findings were published in the journal Environmental Health Perspectives.