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It's the first child for the "Big Love" star

Her engagement to Thomas Sadoski was announced in September

CNN  — 

“Mama Mia!” Amanda Seyfried is having a baby.

The star of “Mean Girls” and “Big Love” debuted her baby bump Tuesday at the launch of Givenchy’s new Live Irrésistible fragrance.

It was announced in September that Seyfried was engaged to actor Thomas Sadoski.

The pair performed together last year in the off-Broadway show “The Way We Get.”

They will also be seen in the forthcoming film “The Last Word.”

It’s the first child for Seyfried and Sadoski.