She's kept a very low profile since becoming a mum but now Scarlett Johansson has finally opened up about all things babies and breastfeeding, in an interview with veteran broadcaster Barbara Walters.

The 30-year-old actress and her French journalist partner Romain Dauriac welcomed their daughter Rose Dorothy into the world on September 4, triggering an experience of parenthood that Johansson describes as "wonderful" and "overwhelming".

"It's wonderful. It's very, very magical - and exhausting," she tells Walters, in an ABC broadcast airing this Sunday titled The 10 Most Fascinating People of 2014.

"The love is just unbelievable. It's very overwhelming."

The Avengers star said she had embraced breastfeeding.

"[I do] the whole bit," she told the host. "I'm nursing and I love it. It's the best way to get back in shape."

The mum had briefly talked about her life as a mum before, in comments to Germany's Gala magazine last week.

"She smells sweet, totally," she said, speaking for the first time since becoming a parent. "I can't quite describe it, but it really makes you euphoric.

"It's exhausting in the most wonderful way. I never thought how much sleeping through the night would mean to me. I still lack experience. Right now I'm just trying to manage. You have to first learn the ropes."

Scarlett is said to have tied the knot with Paris-based Romain, 31, in a secret ceremony in October. 

The pair exchanged vows in an undisclosed location in the States, according to a report in the New York Post. 

"Scarlett and Romain were married in a very intimate ceremony after the birth of their daughter," a source told the newspaper's Page Six section. "They kept the wedding a big secret because they both wanted privacy."

The couple began dating in November 2012,  a year and a half after Scarlett divorced her husband of three years, Ryan Reynolds. They got engaged last year and the actress fell pregnant in January.

"He’s my buddy," she previously said. "Being engaged is an exciting time to enjoy and to really savour."

See Scarlett's style evolution here. 

Barbara Walters' The 10 Most Fascinating People of 2014, airs Sunday on ABC at 9pm

Photos: Rex Features and Getty Images