Beyonce Knowles expects motherhood to be "difficult".

The 'Halo' singer is expecting her first child with husband Jay-Z and although she can't wait to welcome the new arrival to their family, Beyonce admitted she is worried about getting on her child's nerves.

She told '20/20': "It's exciting! I know it's gonna be difficult at times. I know that, like my mother, I'm gonna get on my child's nerves [but] I'm just ready! I'm ready for the next chapter."

Beyonce, 30, also revealed she has tried to control her pregnancy cravings because she is determined not to pile on the pounds.

She added: "I've been really conscious [about food. I've been trying my best not to lose control.

"Because I've met so many people that say, 'My second baby, my third baby, I've learned my lesson.' So I haven't been going crazy. I know it's important that I don't lose myself."

Beyonce, 30, has previously spoken of how she feels it is the right time for her to have a baby now as she has achieved so much in her music career.

She said: "My husband and I have been together for 10 years - all of my 20s - and I just feel like it's time and I'm very grateful that God has blessed me with the biggest gift any human being can have. I think because I've accomplished a lot of things for myself and I really know who I am, I didn't rush into anything. If it's any time, right now is the time, and I'm so happy."