So she lived for nearly two decades without realizing that she had a bonus vagina, and it turns out that's typical. We spoke with a gynecologist, -- pseudonym Virgil Ina, MD. -- and he told us that Vaginal septums often go undiagnosed, well, forever. "This is definitely one of those things that can fly right under the radar for someone's entire life. A lot of them aren't found until pregnancy, or until someone dies and gets an autopsy."

As he explained it, developing female fetuses have two ducts on either side of the body, "kind of like pool noodles." These ducts eventually fuse during development, but there's sometimes a failure to fuse, and that fetus winds up with duplicate parts. Dr. Ina sent us this helpful picture:

Via How-treat.comSorry, Guy-Who-Came-Here-Hoping-For-Pictures. This is as explicit as it's gonna get.

Kelsey's particular flavor of vaginal septum looks completely normal on the outside. She has a small flap of skin separating one vaginal opening from the other, sort of like a trick door in a magician's closet. Depending on which side of the flap you enter from, it felt like a Standard Issue Vagina, even to a doctor. "... you can do an exam on one side, see a perfectly normal vagina and uterus," says Dr. Ina. "And then another person pushes the tissue to another side, ends up in the left vagina and sees a perfectly normal cervix and vagina. It can be very discrete and hard to gauge."

But wouldn't the person, uh, eventually figure it out herself? As Kelsey says, "I masturbated. Who doesn't? But I've got short arms ... I couldn't reach all the way down there, so I had to wait until I had a doctor to find it. It doesn't change the outer structure -- outside is normal, the inside is doubled. So I only have one clitoris, unfortunately."

Keith Brofsky/Photodisc/Getty ImagesSo no extra fun bits, but twice as many ice-cold speculums. Hoo. Fucking. Ray.

Kelsey's case is surprisingly common; about one in 200 women have some variation of this deformation. And believe it or not, it can get more complicated than having two vaginas ...

Once Kelsey tested positive for 200 percent of her lifetime-recommended allowance of vagina, the doctors had to see if any of her other parts had doubled up in the womb. "It turns out that I have one uterus, separated by a septum," she says. Essentially, her uterus is divided into two sections -- one per vagina. But there is a variation of her condition called "double uterus" or uterus didelphys. Our other source for this article, Carly, wound up pulling this card from the great Grab Bag of Bits that our genes occasionally prank us with.

She discovered her condition at age 17. "My gynecologist brought my mom in and said, 'I need to tell you something.' I was like 'Oh fuck, I'm pregnant' at first." But it turned out that she wasn't pregnant; she had two internal baby factories rather than the industry standard of one. Carly was distraught at first. "I asked my mom if she did coke when she was pregnant with me. She didn't find that funny." [Editorial Note: Carly would like us to add that her mom was definitely not on drugs during the pregnancy.]

The question on most of your minds right now is probably, "Can she get pregnant in both uteri at once, resulting in some sort of body-destroying, Alien-type birthing?" Well, we asked Dr. Ina most of that question. "... both [uteri] are viable. Both certainly can be viable and ovulate at the same time, and allegedly this can get very dramatic. You can get two pregnancies that aren't exactly timed together. And they can be from different fathers as well."

Wavebreakmedia Ltd/Wavebreak Media/Getty ImagesWhich could make for one hell of an interesting Lamaze class.

Unfortunately, having two ovens in which to cook buns can actually make the whole person-baking process even more difficult, even with one father ...

Dr. Ina went into more detail: "Because of that confined space, [there is an] increased risk of a uterine rupture, which is a profoundly painful complication. The upper portion of the uterus tears before the baby can exit." He also pointed out that those double uteri still share the space of one uterus. Carly isn't twice the size of a normal person, after all. "As a result of that, you can have miscarriages because there's not enough room in whatever side gets pregnant. You can have intrauterine growth restriction, so the baby is abnormally small. And because there's extra pressure ... the baby can be pushed to term before its ready."

Photodisc/Photodisc/Getty ImagesWhich, as you'll recall, is a bad scene for everybody.

Carly isn't planning to have kids yet, but she admits that she's worried her condition will make it impossible. Some of that is made more difficult by the rareness of her condition. For example, while she lived in New Jersey, Carly says that her gynecologist was "absolutely brilliant" and helped her understand a lot about what was going on inside her dual baby chambers. But today Carly lives in rural Colorado. "The doctors here tried to tell me I only have one uterus ... they've never seen it before."

Keith Brofsky/Photodisc/Getty Images"Sorry, can't have more than one. It's right here on the form."

Unfortunately, Carly and Kelsey get painfully regular reminders of their conditions, because ...

Yes, twice as many vaginas or uteri can mean living through two periods at once. Remember that that's how Carly first found out about her condition. The gynecologist visit that led to the discovery happened because her mother insisted that Carly got "crazy" during her period and wanted her checked out. But Carly had a good reason for said craziness:

"I was getting two periods in a month's span. That was pretty shitty. But the worst thing was trying to use a tampon. My mom was like, 'Just put it in!' and it hurt so much, because I kept hitting the septum. Eventually I figured out how to slide it into one side or the other. But how do you explain that to everyone?"

Medioimages/Photodisc/Stockbyte/Getty Images"'Comfort glide' my ass, Playtex."

Kelsey isn't spared this particularly shitty side effect, either:

"I actually get two menstrual cycles. So they either happen in shifts [where] I have one, wait a week, and then have another, [or] one period will happen and it'll be months before I have another ... the longest time I didn't have one was six months. I was so scared I was going to end up on that 'I didn't know I was pregnant' show. The unpredictability is the worst part. There'll be a really long one, no period for almost a year, and then two right back to back. This one time, I had a period and it got me really badly sick -- lots of blood in the other uterus. It was not a fun time."

Dr. Ina was a little more colorful with his description. "If [a woman has] two uteri and their vagina is split ... it's a double-barreled shotgun, basically. They need to use two tampons for adequate protection." That's right: A medical doctor described twin menstruating vaginas as a double-barreled shotgun.

Exclusive Visual/iStock/Getty Images"Which is also what it will feel like your stomach got shot by."

To be clear, being adequately protected doesn't mean being secure from pain. Carly's lonely single vagina has to deal with two menstruating uteri, and no amount of tampons can prevent her nightmarish cramps. "I have the most intense cramps ... two [uteri] contracting at once. The pain [is so bad] that nothing, not one thing except for my medical marijuana, has helped me with that. It's literally the only thing that helps. I've tried Advil, prescription-strength Ibuprofen, Aleve, Motrin ... Ponstel just made me cry every day. It was awful."

Unfortunately, Carly and Kelsey also have to deal with some awkward social problems, which no amount of marijuana -- medicinal or otherwise -- can alleviate ...