Jenn Cusimano, from Canada, decided to proudly post her ultrasound in a Facebook group she had joined with women who were all expecting.
But when she did, one of the mums-to-be came forward to say her ultrasound looked the same.
"One women noticed and said 'Wow doesn't this look EXACTLY like mine'," Cusimano wrote on Facebook.
"We came to find out we were both from Oshawa and both went to the same clinic one month apart."
Cusimano said the two mums phoned Babyview 3D Parental Imaging Clinic, where they had their ultrasounds.
The mums were offered free sessions to have another 3D ultrasound.
"I am livid," continued Cusimano.
She later posted an update on 18 May claiming there were now 11 women who had come forward to say they have experienced similar problems.
Cusimano set up a Facebook group 'Babyview 3D Scam', which had 1,237 members at the time of writing. She wants women to share their scans so they can see how many are identical.
When contacted by CTV news, Adeel Mir, owner of Babyview Clinic, said the mix-up was due to a "computer glitch", caused by what he suspected was a virus.
"I apologise on behalf of BabyView," Mir said. "We are sorry. Whatever occurred, this was not intentional. It wasn't our intention."
According to BuzzFeed, Babyview offered to do rescans or to give people refunds.
The Huffington Post UK has contacted the clinic for further comment.