“Already so in love with you,” she wrote.
In the pic, the 22-year-old model cradles her stomach as she wears a black bikini.
Geary announced in August that she was expecting her first child with Thicke, 40. “Robin and I are very excited to share with you all that we’re having a baby!” she captioned a pic of the sonogram at the time. “The due date is March 1st, Alan’s birthday!” (Thicke’s famous dad, Alan Thicke, died at age 69 in December 2016.)
The couple went public with their relationship at the Cannes Film Festival in May 2015.
The “Blurred Lines” singer began dating Geary shortly after his ex-wife Paula Patton filed for divorce in October 2014. The exes are parents of 6-year-old son, Julian.
For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!