"My Mirena was found behind the placenta."

When Lucy Hellein of Alabama in the US fell pregnant, no-one was more surprised than her and her husband.

After all, once you have a Mirena IUD inserted, both mind and body reject the possibility of pregnancy with the fervent determination of someone confidence in their next life stage.

And despite boasting a 99 per cent efficient at preventing pregnancy – as stated on their website –  the Mirena didn’t quite work its wonders on the mum-of-two.

Because if it did, Lucy probably wouldn’t have given birth to a healthy baby boy on April 27 this year.

Posting the news to Facebook complete with a photo of her baby boy Dexter holding the Mirena firmly in his little grasp, Lucy called it as she saw it: A “Mirena fail”.

The post, which added the “Mirena [was] found behind [her] placenta” has since been shared nearly 70,000 times.

Talking to Metro about the birth, the now mum-of-three says she assumed she was only a few weeks along when she discovered the pregnancy. She was actually 18 weeks pregnant.

“I found out I was pregnant in December and I’ll admit I was scared because of the Mirena.

“My Mirena was no where to be found on ultrasound so my OB assumed that it had fallen out, but I wasn’t convinced,” she told the news outlet.

When discovering her announcement was soon going viral, Lucy added more detail about the birth experience.

“For those wondering, no I did not push him out, he was a scheduled c-section. My daughter was an emergency c-section, so I had this one scheduled primarily because I didn’t want to risk the possibility of going through another emergency c-section. During the c-section my OB planned on searching for the MIA Mirena as well as remove my Fallopian tube (shutting down my end of the baby factory),” she wrote.

Despite the fact the pregnancy wasn’t planned, Lucy says she now wouldn’t change a thing.

“Although he wasn’t planned, my family and I feel incredibly blessed,” she told Metro.