Johansson and Jost engaged last May after dating for two years. The couple has often been seen spending time with Johansson's five-year-old daughter, whom she shares with ex-husband, journalist Romain Dauriac.
Scarlett donned a pearl pink and vibrant purple dress, which revealed a floral tattoo running down her back.
Scarlett Johansson has reportedly married her boyfriend Romain Dauriac in a secret ceremony.
The baby was wrapped up in a thick coat, pink trousers, a pair of white booties and a white hat covering her ears.
Actress Scarlett Johansson had recently said she hates being a sex symbol.
This will be the first child for the 29-year-old Avengers star with French journalist Romain Dauriac.
Scarlett Johansson says her fiance is her best friend but they don't want to rush for marriage.
Actress Scarlett Johansson, 29, recently shifted to Paris with her fiance.
Johansson likes to work out before heading out for a holiday so that she can eat whatever she wants guilt-free.
The 28-year-old actress confessed that one thing she doesn't like about herself is her impatience.