The AP reports that "mother and daughter are doing well."
The 29-year-old actress kept a low profile prior to giving birth, last stepping out in New York City in July sporting a new mom-proof pixie hairdo.
In an interview with Vogue, the sex symbol gushed about her groom-to-be, telling the mag it's easier to be with a non-actor like her French journalist beau.
"It is [easier], but it's more than that," Johansson said. "We do different things. He's in the whole art-scene world. So it's nice, because we can enjoy each other's worlds, but we don't have our crazy conflicting schedules and all that other stuff to contend with."
Johansson was previously married to Ryan Reynolds for two years until divorcing in 2010.