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No stranger to working while pregnant, Reese Witherspoon braved the hot Georgia temperatures on the set of her upcoming flick, "Devil's Knot," in Atlanta on Thursday.

With her baby bump on full display, the "This Means War "actress, who is pregnant with her third child and first with husband Jim Toth, wore a short-sleeved, loose-fitting polka-dot ensemble and stayed hydrated between takes by sipping a giant ice-filled beverage.

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The film, based on the 2002 best-seller by Mara Leveritt and starring Oscar-winning "The King's Speech" actor Colin Firth, 51, tells the story of three teenagers (later dubbed as the West Memphis 3) falsely convicted of killing three 8-year-old boys during a satanic ritual. After spending 18 years in jail, the defendants were finally freed in August 2011.

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Witherspoon, who plays the mother of one of the victims, only recently opened up about her pregnancy.

"I'm feeling very round tonight," the mom to daughter Ava, 12, and Deacon, 8 (her kids with ex-husband Ryan Phillippe) told the Chicago Sun Times on June 23.

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"After I finish [Devil's Knot], I'm going to take a little time off -- and go have a baby!" she added.

Always pregnant and working, Witherspoon walked the red carpet in 1999 to promote her film "Election," while pregnant with Ava. Four years later, she showed off her baby bump while pregnant with Deacon at the NYC premiere of "Legally Blonde 2: Red, White and Blonde."

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