Chrissy Teigen has been hospitalized for excessive bleeding during pregnancy

• Model and TV personality Chrissy Teigen is in the hospital due to severe bleeding during her third pregnancy.
• She said her future son is strong and healthy, but his "house," or her placenta, is very weak.
• Extreme bleeding after early pregnancy is often due to a problem with the placenta, or the organ that delivers nutrients and oxygen to the fetus and removes waste.

Chrissy Teigen is in the hospital due to excessive bleeding about halfway through her pregnancy, the model, cookbook author, and television personality said in a series of Instagram Stories Sunday.

She's expecting her third child with singer-songwriter John Legend. The couple was surprised to learn she got pregnant naturally since their first two children were conceived through in-vitro fertilization.

Teigen, 34, told followers not to feel sorry for her since she feels good and her son-to-be is still healthy, and requested that medical professionals refrain from giving her advice or trying to diagnose her. "All it does is make me feel really anxious and nervous like I did something wrong," she said.

Extreme bleeding later in pregnancy often occurs when there are problems with the placenta.

Teigen said her son is strong but his 'house' (her placenta) is very weak

In her Instagram Stories, Teigen said she's been on "super serious bed rest" for a few weeks and has been bleeding consistently for a little less than a month.

Her hospital stay was prompted by an even heavier blood flow. It was "like if you were to turn a faucet on low and leave it there," Teigen said, adding that it's been hard to come to terms with since she feels really good.

"It was at the point today where it was just, like, never stopping bleeding. And that's, obviously, very bad," said the mom of Luna, 4, and Miles, 2.

Teigen said her future son is healthy, and growing stronger and moving more and sooner than her other kids, but her severe bleeding is due to a very weak placenta. "Basically, he's the strongest, coolest dude in the sh--tiest house," she said. "So, his house is just falling apart."

Teigen said her placenta was weak to begin with, so "he didn't have the strongest chance at the very, very beginning."

The host of "Lip Sync Battle" said there's not much she can do besides make sure the baby-to-be is surrounded by plenty of fluids and that she's resting as much as possible.

"I'm in that weird in-between time of it being really dangerous to try anything," she said. "Basically if I can make it through the next few weeks, if little boy can make it through the next few weeks, then you know, we can go from there and be able to get through the danger zone or whatever. But we have to get through this first."

"So yeah, it is scary, but it's scary in a way where there's just nothing to do," she said, urging people not to attempt to give her advice or diagnoses since her medical team is on top of it and knows much more of the story. "We're trying everything we can," she said.

Extreme bleeding after early pregnancy is often a problem with the placenta

According to the American College of Obstetricians and Gynecologists, severe bleeding later in pregnancy can occur when there's a problem with the placenta.

The placenta is the organ that delivers oxygen and nutrients to the fetus and removes waste. In most pregnancies, the placenta attaches to the side of the uterus and moves with the growing uterine muscle toward the top of the womb as time goes on, allowing the cervix to open for delivery.

Some placental complications that can arise and lead to severe bleeding include placental abruption, or when the placenta detaches from the wall of the uterus before or during birth; placenta previa, or when the placenta sits too low in the uterus; and placenta accreta, or when the placenta becomes inseparable from the uterine wall.

Kim Kardashian has said she had placenta accreta when pregnant with her first two children, leading to multiple surgeries and her decision to use a surrogate during subsequent pregnancies.

It's unclear if Teigen has any of these specific complications, but she's been open in the past about the couple's fertility problems that led them to use in-vitro fertilization for their last pregnancies. It's unclear if or how those treatments may have contributed to her weakened placenta and severe bleeding.

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