American model and TV star Chrissy Teigen has been hospitalised with heavy bleeding after being warned her pregnancy is high-risk.

34-year-old Tiegen is expecting her third child with singer John Legend and was admitted to Cedars-Sinai Medical Center in Los Angeles on Sunday after her bleeding got considerably worse, she told her 31.3 million Instagram followers.

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She added that she had been experiencing a month of bleeding and had already been put on strict bed rest by her doctors.

Posting from her bed, Tiegen explained her condition and begged her followers not to try and diagnose her.

"We all know I've been on bed rest for a few weeks and that's like super-serious bed rest. I get up to pee and take baths twice a week, no showering, just as little as possible," she said.

"But I was always, always bleeding. I'm about halfway through pregnancy and the blood has been going on for about a month, maybe a little bit less than a month.

"We're talking about more than your period girls, it's definitely not spotting. A lot of people spot but it's usually fine. Mine was a lot.

"Every time I go to the bathroom it would be blood, and honestly just laying there there would be blood."

However, despite the set-back, she revealed she's feeling "really good". "I’m usually at my happiest pregnant, mood wise. That's why it's so hard for me to come to terms with." she said.