Rod Stewart and his wife Penny Lancaster, who is expecting their second child, have revealed they turned to IVF after a long battle to conceive. They tried for two years to give their son Alastair a sibling before seeking medical help.

Speaking in Hello! magazine the couple revealed they spoke to fertility experts in the US and UK.

Lancaster said hearing her son’s joy at the news made the effort worthwhile. She said: "Our son's happiness made all the IVF treatments worthwhile."

Lancaster was told she had very high mercury levels in her system as a result of her love of fish which she believes may have contributed to their problems. She cut seafood from her diet and after her third IVF cycle found she was pregnant.

Recalling the moment she said: "I couldn't believe it. I burst into tears. I called Rod when I was still sobbing. Rod said, 'I'm in the middle of a restaurant in Russia, crying'. I kept pinching myself. Neither of us could believe that it had finally happened."

Stewart said: "IVF can be stressful, especially for the woman with all the hormone injections and procedures. When the first attempt didn't work, I said to Penny, 'don't worry, we'll just keep trying'."

Stewart has seven children - he had a son and a daughter with first wife Alana Hamilton, and a daughter in 1987 with Kelly Emberg. He had two children during his marriage to Rachel Hunter and he also had a daughter in the early 1960s who was adopted.