What Kristen Bell did when her kids accidentally caught her and Dax Shepherd having sex.

With her characteristic candour, Kristen Bell has detailed the time her young children walked in on her and husband Dax Shepherd having sex.

While promoting her new film, A Bad Mums Christmas, the 37-year-old mum-of-two revealed on The Talk on Friday her two daughters once found their parents in a particularly compromising position.

When asked about her most embarrassing moment involving her family, the actress was straight to the point: “Oh, they’ve walked in on us having sex.”

After being probed as to how they weaseled their way out of the situation, Bell said she was honest with four-year-old Lincoln and two year-old Delta. Kind of.

“Well, we didn’t, like, continue… we sort of just went like, ‘Hey, what’s up? What do you need? What do you need?’… And then we just said, ‘Mommy and daddy are just going to take a nap for a couple of minutes.'”

Her admission comes just days after the cast of the new film, including Bell herself, Mila Kunis and Kathryn Hahn, appeared on The Ellen DeGeneres show and shared a story about Bell's breast pump mishap while on set.

After Skyping in to a table read for the major Hollywood blockbuster, half way through the meeting, she realised it was time to pump.

She thought, initially, that no one would notice.

“K-Bell’s just on a giant screen Skyped in, and as we’re reading the script, you see her face just getting closer and closer into the screen,” Mila Kunis told Ellen.

"The rest of her body just keeps kind of getting out of the screen...And then you hear this," she continued, imitating the sound of a breast pump doing it's thing.

However, Bell said she had no idea she was on a big screen.

"I didn't know I was on a movie projector... I would have loved the heads up," Kristen said, adding she thought by 'Skyping in' her image would only be seen on one person's computer.

"I needed to pump... I'm sorry, but when you gotta do it, you gotta do it!

"I thought, 'They're not going to care and it's not going to be very loud'. I didn't realise I was on a 200-inch screen on speakers in a conference room."