When Jenny Kavanagh, a logistics officer from Twickenham, London, started getting heavy periods, she visited a doctor, fearing that her implanted contraceptive coil was causing the bleeding. To her shock, Kavangh, 45, was informed that her undeveloped twin had been growing inside her for the past four decades and was causing her problems.

In fact, the fetus had a face, eye, tooth, and long black hair.

When the doctors told her the news, Kavangh had a hard time believing it - so they showed her a photo. "The fact that it had long black hair - just like mine - a face, with one eye and one baby tooth makes it more believable. I felt shocked, very scared, horrified, and felt like an alien was inside me," Kavanagh said, according to The Week.

"I feel very lucky that they found it and removed it before it killed me. I try not to think of it too much because I don't want to feel sad about it. If I'm honest, I did feel sad when I first saw it, because of the size and weight of it, it had already been likened to a baby. But I try not to feel sad about it. I try to remember that it had no heart and no brain. And that it would have almost certainly killed me if they hadn't found it and removed it. But in one sense there was grief, mixed with happiness. It was like a baby, but I was still glad it was out of me," she added, The Mirror reported.

"When I showed the picture to my mum she was really sad - saw it as her unborn child, and my unborn twin," Kavanagh said, according to Naij. Kavanagh underwent a three-hour operation to remove her twin and has since made a full recovery.