One night in November, Madi Swegle was making dinner when her period cramps started to come on — and they were intense.
At first, the 24-year-old labor and delivery nurse just thought it was a bad period, she tells TODAY.com. But about an hour later, the cramps got much more painful.
"I usually have pretty tolerable periods. They really have never bothered me that much," Swegle says. "But this was totally different."
She grabbed a heating pad and went upstairs to the bathroom.
"I had my husband bring me some water," Swegle says. "I was nauseous from the pain. I had chills."
Swegle says she sat there for an hour in pain until she felt something "pass" out of her vagina — and she was startled by what she saw. Instead of the multiple clots she was used to seeing with her period, Swegle passed a single placenta-like piece of tissue in the distinct triangle shape of her uterus.
Even with her experience as a labor and delivery nurse, Swegle had never seen anything like it. But as soon as it passed, she felt relief from the pain.
She immediately FaceTimed with coworkers who were just as perplexed as she was but agreed that it looked like a placenta. Eventually, she connected with an OB-GYN who told her that she'd just passed what's known as a decidual cast.
What is a decidual cast?
There are two main things to know about decidual casts right off the bat, Dr. Salena Zanotti, an OB-GYN at the Cleveland Clinic, tells TODAY.com. First, a decidual cast is "extremely rare," she says. And, second, it's not dangerous.
“A decidual cast is pretty much like a replica of the uterine wall,” Dr. Christine Greves, an OB-GYN at Orlando Health Winnie Palmer Hospital for Women and Babies, tells TODAY.com. It’s made up of the tissue that lines the uterus “combined with some mucus and blood,” she says. And, to get it out, the cervix may need to dilate, which can cause discomfort, Greves adds. (This may have been the cause of Swegle's unusual period pain.)
Technically, the term "decidual cast" simply refers to tissue that's passed and doesn't contain any signs of pregnancy, Dr. Steven Goldstein, a professor of obstetrics and gynecology at the NYU Grossman School of Medicine, tells TODAY.com. The term is often used in the context of a miscarriage or an ectopic pregnancy, which is a pregnancy that forms outside of the uterus, he says.
If a person recently had a positive pregnancy test and passes a decidual cast that carries signs of a pregnancy, like the presence of chorionic villi, that helps confirm that person actually had an early pregnancy loss, Goldstein explains. In that case, however, what might look like a decidual cast is actually the gestational sac, Zanotti says.
But in other cases, where the tissue doesn't have signs of pregnancy, that person might really be dealing with an ectopic pregnancy. “If you have a positive pregnancy test and the tissue you pass doesn’t have any pregnancy tissue in it,” Goldstein says, “where’s the pregnancy, right?”
When that happens, people may still have bleeding and cramping and pass tissue — the decidual cast — and then the ectopic pregnancy can rupture a week or two later, Goldstein explains. A ruptured ectopic pregnancy is a dangerous complication that requires timely treatment, as TODAY.com explained previously.
In exceedingly rare cases, someone who isn't pregnant might pass a decidual cast the way Swegle describes, Greves says. It's tough to say how common this really is "because no one's done the study," Goldstein says.
What causes a decidual cast?
It’s not always clear exactly why someone develops a decidual cast, but it’s often related to changes in levels of the sex hormone progesterone, Zanotti explains.
During the normal menstrual cycle, changes in progesterone cause the lining of the uterus to start the decidualization process, meaning the tissue will thicken and coalesce. At that point, if you don’t become pregnant, you shed the lining during your period, Zanotti says.
A decidual cast occurs when you shed the lining all in one piece, rather than in multiple pieces. There are only a handful of cases like this in the medical literature, Goldstein says, and almost all of them occur in people using contraceptives.
In particular, there’s an association between people starting or just coming off of progestin-only forms of birth control (like the shot) and decidual casts, Zanotti notes. But that’s not a reason to stop using those highly effective contraceptive options, she adds.
If you have a decidual cast, what should you do?
It’s crucial that anyone who experiences symptoms like Swegle’s take a pregnancy test if there's a chance they could be pregnant — and get in touch with their doctor, Goldstein says. If they're pregnant and experiencing pain like this, especially if it's one-sided pain, that could indicate an ectopic pregnancy, Greves adds.
In some cases, your doctor may want you to save the tissue to have it analyzed, Goldstein says. But Greves and Zanotti both say that's usually not necessary.
Above all, if you have symptoms like Swegle's, you should talk to your doctor to get some guidance, the experts agree.
"Having a decidual cast does not necessarily mean that someone's abnormal," Greves says. "But I do think I'd be concerned enough to prompt someone to get evaluated."
Sharing her story
Swegle shared her story on TikTok and the video now has 1.6 million likes on the platform.
Although she doesn't know exactly why she experienced the decidual cast, she and her doctor think it may have had something to do with the hormonal birth control medications she was taking before undergoing IVF.
Swegle has been pleasantly surprised both at how viral her video went and how supportive and validating the comments have been. But she wishes she'd known more about what she was going through at the time because the anxiety of not knowing only compounded the pain.
"Half of the worst part of it was just not knowing what was going on," Swegle explains. "There was the anxiety of having that pain and being like, 'What the heck is going on with my body?'"
That's the main reason why Swegle decided to share her story in the first place. If she didn't know what was going on, she figures, others probably don't know much about decidual casts either. But knowing would have made the process more tolerable, she says.
The fact that Swegle was so open about her experience will help raise awareness about decidual casts and the importance of noticing changes in your body more generally, Greves says. She hopes it will encourage people to pay attention to their menstrual cycles, and "if it's painful, whether there's a cast or not, reach out to your OB-GYN because you're hurting."
More than anything, Swegle says the experience has been "eye-opening" for her, and she encourages others out there to advocate for themselves. “Looking back on it now, I knew something was off with my body,” she says. “And I really hate that I second-guessed myself about my pain.”
"We know our bodies best," she says. "And if something feels off, something probably is off."