Now that the star is considering baby number three, here are all the facts about this potentially serious — but rare — condition

You aren’t born with a placenta. Instead it develops in your uterus during pregnancy and acts as life-support for your growing baby. Then once delivery is said and done, it, too, is expelled from the uterus. But for a number of women, this doesn’t happen, and instead a potentially life-threatening condition — called placenta accreta — keeps the organ from leaving the body as it should.

Kim Kardashian West, who suffered from placenta accreta during her pregnancies with daughter North and son Saint, has been open about the scary experience.

“My doctor had to stick his entire arm in me and detach the placenta with his hand, scraping it away from my uterus with his fingernails,” she previously wrote on her website of welcoming North in 2013. “My mom was crying; she had never seen anything like this before. My delivery was fairly easy, but then going through that — it was the most painful experience of my life!”

Now that the star is considering baby number three, here are all the facts about this potentially serious — but rare — condition.

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What exactly is placenta accreta?

During a normal pregnancy, the pancake-shaped placenta is supposed to lightly attach to the lining of the uterus, allowing nutrients and oxygen to pass from the mother’s womb to the baby via the umbilical cord. At the time of birth, the placenta detaches itself from the uterine wall and comes out via the birth canal shortly after the baby is born.

“But in rare cases, the placenta will have grown into the wall of the womb itself, preventing it from easily detaching at the time of birth,” explains Jan Rydfors, MD, a board-certified ob/gyn who specializes in fertility and high risk pregnancy and co-founder of the app Pregnancy Companion. “This deeply imbedded and stuck placenta is called a placenta accreta.”

It’s also referred to as placenta increta or placenta percreta, depending how deeply or severely the placenta is attached, according to the American Pregnancy Association.

While it’s still pretty rare — placenta accreta occurs in 3 in 1,000 pregnancies, according to the Society for Maternal Fetal Medicine — it’s on the rise. In the 1970s the incidence was closer to one in 4,000 pregnancies.

It can lead to health risks for the mother and affect future pregnancies.

It’s unclear what causes it.

The number of placenta accreta cases has risen in step with the increase in Cesarean sections, the American College of Obstetricians and Gynecologsists (ACOG) says. That’s because damage to the uterine wall during a C-section seems to play a role in developing the condition.

“The highest risk is when a pregnant woman has had one or more Cesareans in the past,” explains Dr. Rydfors, “and the current placenta appears to be growing over the Cesarean scar.” (In these cases, a third or more of women will have a placenta accreta.)

However, it’s not totally clear why it occurs during a first-time pregnancy.

There aren’t many symptoms.

One warning sign of placenta accreta is bleeding during the third trimester, according to the American Pregnancy Association. But more often, it is symptomless. “Fortunately, ultrasounds and MRIs can often pick up more than 90% of them in the second trimester of the pregnancy,” says Dr. Rydfors.

However, some women aren’t diagnosed until delivery.

It can be life-threatening.

The biggest risk to the mother is severe bleeding that can occur once the placenta is disconnected. “If the placenta accreta is a very minor one—where the placenta is only slightly stuck to the womb—it will usually come out with an extra tug,” Dr. Rydfors says, but more bleeding than average is expected.

But if the placenta is deeply attached, the hemorrhaging can be life-threatening.

Treatment is often surgical.

If the condition is detected before birth (or your risk is high), most doctors will recommend doing an early C-section, explains Dr. Rydfors. “It’s typically performed a month or more before the due date to make sure the delivery happens before spontaneous labor occurs,” he says.

Then, depending on severity, a hysterectomy, with the placenta in place, may be done immediately following birth in order to avoid the severe bleeding from attempting to disconnect it. “The most extreme case I’ve seen is when nearly the whole placenta had grown into the womb, and it [was] literally impossible to separate it,” Dr. Rydfors says. That case required a full hysterectomy to remove both the placenta and the woman’s uterus.

In certain cases, the mother can conceive again.

There are instances (though sadly, they are less common) where the uterus can be spared by using special treatments to remove it, while still trying to control the bleeding. “Not removing the uterus may be an option,” Dr. Rydfors says, “but it’s not risk-free, and it’s often associated with very heavy bleeding and potential scarring inside the womb.”

The good news: Though risk of placenta accreta is high the second time around, a majority of those women who did not have to have a hysterectomy will be able to have another baby.