The Bachelor couple are currently living together in Scottsdale, AZ, and on Sunday, Arie posted a photo of a woman's baby bump in a tight dress on an Instagram story.
The photo featured a woman from the neck down -- showing tips of blonde hair and a rock of an engagement ring on her left hand -- which allowed the pro racing driver's followers to believe Lauren is pregnant with their first child together.
"Secrets finally out, we have a bunny in the oven! @laurenburnham91," Arie captioned the image on Easter Sunday.
About an hour later, Arie responded to his own post, writing, "APRIL FOOLS!"
Arie's joke was deemed insensitive and offensive by others, especially women struggling to conceive a baby.
"You both are disgusting. As someone who struggles with fertility and would love nothing more than to have a baby this is so offensive," wrote one social-media user.
Another person wrote, "Come on. be better than that. It's not a joke for many struggling families to get pregnant, it's extremely expensive and it's heartbreaking. I wish nothing but the best for Arie and Lauren but this is not funny, it's cruel."
One Twitter user went as far as to share a link to a prior ABC News article entitled, "Why you shouldn't joke about pregnancy on April Fool's Day." The article apparently had some good advice for Arie and Lauren!
Arie, 36, appeared to address the backlash, as he subsequently shared a picture of a recipe for a German pancake on his Instagram story, writing, "Sorry if you were offended, but we really are making a Dutch Baby."
Arie then begged Lauren, his runner-up, to take him back, and the couple got engaged during the March 6 The Bachelor: After the Final Rose special. The pair have already begun wedding planning, and kids are definitely in their near future.
"We're both very excited about marriage and starting a family," Lauren, 25, previously told People.
Arie told the magazine he'd love to have between two and four children and he'd feel lucky to have twins right away!