The contraceptive connection behind the rare phenomenon known as a decidual cast

The pain is caused by the womb tightening and relaxing to encourage its lining to shed - a process that happens each month as part of a woman’s menstrual cycle. Picture: Flickr.com

Finding what appears to be a piece of tissue shaped like the inside of your uterus can be terrifying, especially if you've never heard of a decidual cast.

Although rare, medical experts say the phenomenon is becoming more widely recognised, partly because more people are sharing their experiences and because of greater awareness of hormonal contraceptives.

A decidual cast occurs when the entire lining of the uterus is shed in one intact piece rather than breaking apart during menstruation. The result is a piece of tissue that can resemble the shape of the uterine cavity and is often accompanied by severe cramping and pelvic pain.

While it can be alarming, a decidual cast is usually not dangerous. However, experts advise anyone experiencing one for the first time to seek medical attention to rule out other conditions, including miscarriage or ectopic pregnancy.