The UNICEF report also states that South Asia has the largest proportion of babies living in areas where air pollution is at least six times higher than global limits (10 micrograms per cubic metre).
"Not only do pollutants harm babies' developing lungs, they can permanently damage their developing brains, and thus, their futures", Anthony Lake, UNICEF's executive director, said.
Satellite imagery used to assess pollution levels around the world found that South Asian countries accounted for 12.2 million of the total number of affected children but that there is also a growing problem in African cities.
The report entitled Danger in the Air: How air pollution can affect brain development in young children also notes that breathing in particulate air pollution can damage brain tissue and undermine cognitive development - with lifelong implications and setbacks.
Indian and Sri Lankan cricketers playing in Delhi vomited on the pitch during high levels of pollution.
"As more and more of the world urbanises, and without adequate protection and pollution reduction measures, more children will be at risk in the years to come".
The report sets out a range of ways that the impact of air pollution on babies' brains could be lowered.
Damage to the membrane has been linked to Alzheimers and Parkinson's disease in the elderly.
The crisis saw large swathes of north India and parts of neighbouring Pakistan blanketed in acrid air - an annual phenomenon as cooler air traps particles near the ground, cause pollution levels to spike.
The first and foremost step that each one of us should take is towards reducing air pollution as much as possible. "A mask that does not fit the face well won't work".