"I was ready to hand over the crown," Stefani captioned a photo of herself wearing a bejeweled crown. "But I guess I am still queen of the house. #itsaboy #surroundedbyboys."
The post was Stafani's first on the image sharing site, which she joined Thursday.
The No Doubt singer married Rossdale in September 2002. The two are already parents to sons Kingston, 7, and Zuma, 5.
2014: NFL Cheerleaders [PHOTOS]
Soviets call Reagan joke 'dangerous' [ARCHIVE]