What is uterus didelphys? Why some women have two uteruses — and separate pregnancies.

Just as external sex organs such as the labia and clitoris can look vastly different on different people, so can those that are internal.

One instance — albeit extremely rare — is the dual uterus. Known as uterus didelphys, this is “part of a spectrum of disorders that are referred to as Müllerian abnormalities,” says Erin Higgins, an ob-gyn doctor at the Cleveland Clinic, which has a specialized clinic for anomalies of the reproductive tract. The Müllerian ducts are paired tubes that grow into female reproductive organs early in fetal development and form the uterus, cervix, fallopian tubes and upper vagina.

Why does uterus didelphys happen?

This is a “congenital anomaly that someone is born with,” Higgins says. “It’s all about how hormones communicate with different receptors, and where there are absences of one, you can get formation of different reproductive organs. You can have everything from complete uterus duplication ... to something just shy of normal, which is an arcuate uterus [a minor irregularity of the uterus], which is sometimes referred to as a ‘heart-shaped uterus.’”

Dr. Laura Purdy, chief medical officer at Wisp, a sexual health care group, says that “uterus didelphys is rare,” only accounting for 8% of the congenital anomalies of the female reproductive tract and only occurring in 0.3% of the total population. She notes, however, that uterus didelphys is “slightly more frequent within the population of women with a history of abortion and infertility.”

Why someone might develop these congenital uterine irregularities, however, is “not well understood,” says Dr. Beth Oller, family physician at Rooks County Health Center who has treated women with the condition, and it often presents differently in different people.

“There can be two uteruses with one cervix, or there can be two cervices,” she says. “In addition to having two uteruses, and possibly two cervixes, there is also often a vaginal septum, or a wall of tissue that runs down the length of the vagina and creates two different vaginal openings.”

While this vaginal septum is sometimes referred to as “two vaginas,” that’s not exactly the case, as they aren’t side-by-side separate openings or two separate vulvas.

What are the health complications of uterus didelphys?

According to Oller, “With uterine didelphys there is a higher risk of miscarriage, preterm labor, breech presentation, the need for a Cesarean section, pregnancy-associated hypertension, lower birth weight and growth restriction.”

Despite that, she says, “many women with a double uterus have successful pregnancies.”

“I have even delivered babies from someone whose first pregnancy was in one uterus and the second pregnancy in the other,” says Oller. “It isn’t necessary to treat a double uterus unless someone has complications like repeat pregnancy loss, as having surgery to create a single uterus can weaken the uterine muscles.”

It is theoretically possible for a person to develop separate pregnancies in each of their uteruses at the same time, though it’s extremely rare. In 2019, a woman living in Bangladesh with a double uterus gave birth to three babies — first, a baby from one uterus, and then, 26 days later, twins from her second uterus. And in December 2023, new mom Kelsey Hatcher of Alabama, who learned at age 17 that she had uterus didelphys, announced that she'd given birth to twin girls a day apart.

Higgins says that while two completely separate uteruses are a rare anomaly, women who have the more common bicornuate uterus will likely have a pregnancy develop in the more developed “horn” of the uterus.

A vaginal septum can make sex more painful, especially if you are unaware you have one, as OnlyFans model Evelyn Miller, who was diagnosed with uterus didelphys in 2011, explained in an interview with South West News Service earlier this year.

How is uterus didelphys diagnosed?

It can be tricky to diagnose someone with uterus didelphys, because most people are asymptomatic, says Oller.

“Many women do not know that they have a double uterus, especially if there is no vaginal septum, a finding which may be discovered on a routine pelvic exam, or if someone is having pain with intercourse,” she says. “I have diagnosed one patient who had no idea until we got an initial pregnancy ultrasound and found out there were two uteri. Someone with a double vagina may find that when they use a tampon during a period, for example, they still have bleeding, as blood is still flowing from the second uterus and vagina.”

This article was originally published on Sept. 19, 2023 and has been updated.