"So today we went baby shopping with @johnlegend & @chrissyteigen - Kanye and North were a little too quiet," Kardashian wrote on Instagram.
"We found them passed out in the middle of the store."
Teigen, who has been open about her fertility struggles in the past, revealed she was expecting her first child with husband John Legend in October 2015.
"As many of you know, we've been trying to have a baby for a while now," Teigen wrote on the Instagram announcement.
"It hasn't been easy, but we kept trying because we can't wait to bring our first child into the world and grow our family. We're so excited that it's finally happening."
The couple revealed in December they are expecting a girl.