Her followers were quick to point out that Theodore has a few more months to go before his actual birthday.
She later acknowledged that yes, 8 months is not technically a "birthday".
This is the second time in a week Trump's social media accounts have made headlines.
Last Tuesday she was accused of a potential conflict of interest, as she promotes her fashion brand while making political appearances with her father. She was under pressure to separate her business and personal social media accounts.
In a "letter" that appeared on her Twitter and Instagram feeds, the businesswoman's team said that her existing @IvankaTrump accounts - which have 2.4 million and 1.9 million followers, respectively - will now be for "personal" use.
All information related to her clothing and jewellery brands, meanwhile, will appear on @IvankaTrumpHQ accounts.
"As a private citizen, with full awareness of her heightened visibility, she will broaden her efforts to take a stance on issues of critical importance to American women and families," the statement said.
"Our company's mission is not political - it never was and it never will be - however, Ivanka, personally, has an increased opportunity to advocate for women and be a positive force for change," it added.
Ivanka Trump, The Trump Organisation's vice president of development and acquisitions, and her two brothers, vice presidents at the conglomerate, have been called upon to manage their father's fortune and affairs during his tenure at the White House.
