Former pop princess Britney Spears may be putting her unborn baby at risk by recently dying her blonde hair jet black.

Spears was spotted in New York City with her son, Sean Preston, and her new look - which has landed her in hot water once again with her critics.

Concerns have arisen that some hair dyes contain chemicals that could cause birth defects.

According to the Daily Mail, Professor James Walker, of the Royal College of Obstetricians and Gynecologists, said: "It depends on the sort of dyes that she uses, but most modern hair dyes are safe as it's very hard to absorb a lot into the skin."

Last month Spears was photographed almost dropping her baby on the pavement while holding him. She was also caught by paparazzi sunbathing her bump for two hours in the 80-degree heat near her home in Malibu, California.