She gave birth just nine weeks ago but was back on the showbiz scene immediately to promote her award-nominated turn in Gone Girl.
And because of that Rosamund, 36, has had to take any opportunity she can to breastfeed, including at the BAFTA Awards on Sunday night, where she revealed she got 'butt naked' to feed her son Atom.
Speaking to chat show host Ellen DeGeneres for Thursday's show, she said: 'At the BAFTAS Sunday night. I was like oh, and I just roped up into the chairman of the Royal Opera House’s office and just tried to put on the robe and I couldn’t do the buttons, and whipped it off. And I was just sitting there butt naked with the double breast pump.'
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Working mother: Rosamund Pike has admitted she stripped off backstage to breastfeed her son Atom at the BAFTAs in London on Sunday
She jokingly added: 'And if this guy had seen the kind of scene in his office, it was as underhand as if we’d been taking drugs or something. But it was the most innocent.'
Rosamund has been one of the first stars to hit the red carpet at every awards show so far this season, surprising when nominees like herself usually come much later.
But she admitted that she has been showing up early so she has time to feed her son before the shows start.
Who would have guessed: Not long after this picture was taken, Rosamund was backstage feeding her son
Proud mama: Rosamund has admitted she has become inseparable from her son and brings him everywhere
Rosamund explained: 'It’s kind of like it’s a funny kind of rock and roll. I do the red carpet. I get there really early. I’m the sort of really uncool one who shows up very early for carpet. First off, I’ve never been early for anything in my life, right. And then I disappear off and I set up a sort of station backstage somewhere.'
Meanwhile, with Academy Awards, for which she has been nominated in the Best Actress category, just 10 days away, Rosamund got a helping hand from Ellen DeGenres when it came to picking out her dress.
Ellen presented the blonde beauty - who was wearing a Chloe dress from their Pre-Fall 2015 collection - with a custom-made gown featuring a built-in breast pump, which prompted Rosamund to laugh delightedly.
Unusual: Ellen DeGeneres presented Rosamund - who was wearing a Chloe dress from their Pre-Fall 2015 collection - with a special dress featuring a built-in breast pump for the Oscars
The gown, a beige lace number, was fitted with all of the paraphernalia needed by the star to express milk for her newborn son, Atom.
After giving birth to her first son Solo in 2012, Rosamund went on to have another boy in December with Old Etonian adventurer and reformed heroin addict Robie Uniacke.
Sticking to the singular theme, a source told Daily Mail that the couple have called their newborn Atom because Rosamund found her home birth 'so easy and elemental'.
And Rosamund has become inseparable from her son, telling news.com.au: 'I am not very good at delegating. And I don't want to miss my child's first few months because I have got somebody helping while I gallivant off to events.
'So I am taking the baby to meetings … I rock up and people are like: "oh, you brought your baby".'
Happy family: After giving birth to her first son Solo in 2012, Rosamund went on to have another boy in December with Old Etonian adventurer and reformed heroin addict Robie Uniacke
'Obviously I have help for the nights of the actual shows themselves.'
While Rosamund is unlikely to wear Ellen's bizarre dress, she recently explained she wore an extremely revealing dress to the Golden Globes because she didn't 'fit into any of the dresses' she tried on.
She told ABC News: 'You’ve got to take that knife out and start slashing,” she said, referring to the dress’ unique style.'
Revealing: Rosamund recently explained she wore an extremely revealing dress to the Golden Globes because she didn't 'fit into any of the dresses' she tried on
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