The presenter's TV show Extra broke the news, revealing that Teri and her partner Clark Mallon had become parents to a daughter on Monday, 9 March.
Baby Seymour-Mallon was born in Los Angeles.
No name has been released.
Aww! Congratulations to Terri and Clark! A play friend for Simon's son Eric Cowell, who turned one in February.
Just three days before she gave birth, US-based Terri had shared an image to Twitter showing herself balancing on an exercise ball. The caption read: "Nearly there! #Bump."
Terri Seymour (@TerriSeymour) March 7, 2015
Terri, 40, told People earlier this year that she was thrilled to be having a daughter, admitting: "Deep down inside I think I've always wanted a baby girl."
The star has looked gorgeous throughout her pregnancy, as seen in the above picture of her attending a post Golden Globes party earlier this year.
We can't wait to see a pic of the little one!
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