Gwen Stefani has blamed her recent lack lustre tour performances on having to keep her pregnancy secret.

The former No Doubt star found out she was expecting her first child with Bush singer Gavin Rossdale just before she hit the road, but kept the happy news a secret.

By the time she approached the end of the tour Stefani found herself struggling to keep up.

She confesses, “I found out I was pregnant right before I went on tour and I was like, ‘No, I have nine costume changes and high heels and bathing suits.’

“All I could think of was being on the tour and being pregnant but not being able to tell everyone and not really feeling like myself.

"I just wanted to say, ‘You don't understand, I am really sick, and wanting to be like, ‘You guys, you don't understand...’ I was four-and-a-half months pregnant the last show. It was a little bit ridiculous."

Stefani is due to give birth in June.