Speaking about the vocalist, who also has five-year-old daughter Blue Ivy with husband Jay Z and the unique creation to Vogue.com, the creative mastermind said: "It's particular mainly because her measurements were constantly changing."
And the entrepreneur found it "challenging" keeping the news Beyoncé was pregnant a secret.
He explained: "And also keeping it a secret from my collaborators became increasingly challenging as she grew."
And the 'Run The World' hitmaker, who recruited the help of Peter to design the outfits for her 2013 'Mrs. Carter' tour handpicked the mogul again for the musical extravaganza because she knew he was going solo and wanted to be the first person to adorn his collection.
He continued: "Beyoncé and I have a long working relationship. I think she wanted someone she trusted and connected with on several levels, and felt the 'Lemonade' dress had particularly been that.
"She also knew I was going solo and liked being the first to wear my new collection. Also we both love yellow!"
And Peter has revealed he embellished two cherubs on the hip area of the bejewelled garment because he wanted to create a story with the gown.
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He explained: "I like creating stories within a garment. It was a fun way to celebrate the moment for her."
Peter took to social media to showcase his sketches of the intricate garment.
He captioned the post: " PETER DUNDAS X BEYONCÉ #FirstLook#grammys2017 #beyonce @beyonce#lovedrought #PeterDundas#houseofmalakaixpeterdundas #Proudly announcing the very first #peterdundas eponymous collection look specially made for our muse queen Bey #thankyou @marnixmarni."