Miley Cyrus and Demi Lovato front new feminine hygiene campaign

Miley Cyrus and Demi Lovato have shared the "embarrassing" stories of their first periods in a bid to encourage young girls to embrace the natural menstruation process.

The pop stars, along with rocker Noel Gallagher's model daughter Anais, have joined forces with officials at innovative sanitary towel brand betty to launch the Find Your Fit campaign, allowing girls to choose the size of pad best suited for them.

As part of the advertising push, Miley and company have opened up about how they reacted when they first started menstruating in the hopes of helping others.

The Wrecking Ball hitmaker remembers pleading with her mother, Tish, to help her after starting her period while on the set of her hit Disney show Hannah Montana.

"It was so embarrassing, but I couldn't leave," she recalls. "And I was crying, begging my mom, 'You're going to have to put the tampon in. I have to be on set.'"

Meanwhile, Demi, who celebrated five years of sobriety on Wednesday (15Mar17), reveals she was teased relentlessly by her own family when she had her first period.

"I told my mom and my sister and they actually embarrassed me so bad (sic)," she says. "My sister folded a poster board in half and made a card out of it and drew pictures, and it said, 'Happy Period Day!' She drew stick figures and kisses, and she used red markers... I have a pretty good sense of humor, so on one hand, I was totally embarrassed, and on the other, I thought it was awesome."

And Anais Gallagher, 17, tried to play it cool as she started bleeding at school, adding, "(I) desperately wanted it to not be a big deal."

Bosses at betty hope the stars' stories will help to inspire confidence among teenagers and pre-teens during puberty, while their new sanitary towel sizes are aimed at improving comfort for girls during menstruation.