Stewart and Lancaster's IVF baby

Stewart and Lancaster's IVF help to help them conceive

Rod Stewart and Penny Lancaster have spoken about how they had to resort to IVF to help them conceive.

Lancaster was having troubles falling pregnant, partly due to the high levels of mercury in her system. The 39 year old loves fish and follows a low carb, high protein diet which meant her mercury levels soared.

Her doctor advised her to decrease the amount of fish she eats and after 2 months her levels returned to normal.

Lancaster and Stewart have one child together, 4 year old Alastair, who is said to be overjoyed at the idea of having a little brother or sister.

Rod Stewart, 66, has said that this will be his last child. The rocker already has seven children, including the eldest, Sarah Streeter, who at 46 is 7 years older than Penny Lancaster.