"As some of you may know, Gerard and I are very happy awaiting the arrival of our first baby!" Shakira announced in a Wednesday afternoon posting on her website.
"At this time we have decided to give priority to this unique moment in our lives and postpone all the promotional activities planned over the next few days. This means I will not be able to be a part of the iHeartRadio Music Festival... this weekend... I'd like to thank Clear Channel and my fans for their constant love and understanding. Big kiss!"
Shakira and Pique, a 25-year-old professional soccer player who plays for Spain's FC Barcelona team, began dating in early 2011. The baby will be the first child for both.
NBC announced Shakira and Usher will replace Aguilera and fellow The Voice coach Cee Lo Green as coaches on the fourth edition of The Voice on Monday.
"We are thrilled to welcome Usher and Shakira to The Voice. The addition of these popular iconic artists continues the tradition established by Christina, CeeLo, Adam and Blake," NBC Entertainment chairman Robert Greenblatt said.
NBC cited The Voice's new twice-a-year broadcast schedule as the reason why Aguilera and Green -- who are both expected to return to the show down the road -- will be taking the reality singing competition's fourth edition off.