Extract from the Telegraph:
"Expectant mothers can expose themselves to the higher risk by drinking the water, swimming in chlorinated water, taking a bath or shower, or even by standing close to a boiling kettle, say researchers.
The finding, based on an analysis of nearly 400,000 infants, is the first that links by-products of water chlorination - chemicals known as trihalomethanes, or THMs - to three specific birth defects.
Exposure to high levels of THMs substantially increased the risk of holes in the heart, cleft palate and anencephalus, which results in the absence of a major portion of the brain, skull, and scalp."
Best to read the whole of the article in the Telegraph.