A new study revealed that expectant mothers who drink or even bath in tap water can double up the risk of grave heart and brain problems in their unborn babies.

The study published in the journal Environmental Health relates byproducts of water chlorination, chemicals known as trihalomethanes (THMs) to increased the risk of holes in the heart, congenital disorder and anencephalous, which is characterized by partial or total absence of a brain.

Researchers who studied around 400,000 babies born in Taiwan discovered that high levels of chlorine by-products in tap water could have an effect on the growth of babies in the womb.

The worrying result suggested that pregnant mothers expose themselves to the higher risk by drinking the water, swimming in chlorinated water, taking a bath or shower, or even by standing near to a boiling kettle.

Professor Jaakkola of the University of Birmingham's Institute of Occupational and Environmental Medicine, the author of the report, stated, “The biological mechanism for how these disinfection by-products may cause defects are still unknown.”

“However, our findings don't just add to the evidence that water chlorination may cause birth defects, but suggest that exposure to chlorination by-products may be responsible for some specific and common defects,” Professor Jaakkola added.

He also said though chlorination has been a major public health success by cutting waterborne diseases that earlier study may have missed this effect by not using specific categories of birth defect.

He further added, “While the benefits of water chlorination are quite evident, more research needs to be carried out to determine these side-effects.”