The Hollywood actress got engaged to Romain six months ago and now they are set to become parents, according to US websites People.com and E! Online.
Reveal has contacted Scarlett's rep, although she had no comment to make when approached by other news outlets.
Although the couple got engaged last year, Scarlett and French journalist Romain have not rushed into planning their big day.
In a recent interview with US TV show Good Morning America, Scarlett admitted: "I'm not doing any wedding planning."
Scarlett and Romain confirmed they were dating in November 2012. Last week, the couple were pictured at the 39th Cesar Film Awards in Paris, France.
The 29-year-old actress kept covered up in a navy blazer and coordinating trousers.
Celebrities who have announced baby news in 2014:
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