The McFly drummer, 29, kept a protective arm around Izzy's shoulders when they attended The Baby Show at Olympia, London, on Friday (23 October).
Former Escala violinist Brittany 'Izzy' Johnston, 31, showed off her blossoming baby bump months ahead of their January due date.
Wearing a tight white T-shirt dress with denim shirt, teamed with black leggings and comfy black Uggs, mum-to-be Izzy looked fresh as a daisy as she shopped for baby things at the huge event - a dream for first time mums.
Harry and Izzy recently celebrated 10 years together and shared loving messages to each other on social media.
Posting a throwback picture from their early days, Harry wrote: "10 years ago today @izzyintheattic and I shared our first kiss on the Wonderland tour in Cardiff. A whole decade of laughter, love and happiness. Love you Iz xxx."
Izzy, in turn, wrote: "10 years ago tonight I shared my first kiss with @juddymcfly Thank you for filling my life with love, laughter and happiness, you are my everything xxx."
The couple first announced they were expecting a baby back in July.
The 'Five Colours In Her Hair' musician - who won Strictly Come Dancing in 2011 - said: "Izzy and I are so happy and feel truly blessed to be able to share with you that we are expecting our very own little miracle #BabyJudd."
They became engaged in May 2011 in St Lucia when Harry proposed over a candlelit dinner. The musicians married in Harpenden on 21 December, 2012.
In a recent interview, Harry revealed they conceived with the help of IVF.
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