In honour of the special occasion, the mother-of-three uploaded a precious picture of herself bonding with her baby daughter Nancy whilst holidaying in sunny Menorca.
The star, who welcomed baby 'Nance' back in July, beamed in the photo as she cradled her tiny tot in the glorious sunshine. For the special milestone, Nina opted for a vibrant Hawaiian shirt which she wore layered over what appeared to be a khaki swimsuit.
She wore her brunette locks down loose, flipped over to one side and shielded her eyes from the sun's harsh rays with a pair of stylish wayfarer sunglasses.
Nancy, meanwhile, looked as adorable as ever in a white, summer romper dotted with a delicate peach-hued pattern.
"It's my birthday," Nina wrote in her caption. "43 bringing extra gratitude, a few extra lbs, and one extra (extra) midlife Dad-on-hols Hawaiian shirt."
Nina's fans and friends raced to the comments section to share their birthday well-wishes. One follower penned: "Looking fab Nina... Hope it's been brilliant," while another chimed in: "Happy birthday Nina, lovely photo of you and your daughter."
A third gushed: "Awwwww happy birthday ma love [heart emoji] doing it in style and a fourth commented: "Happy birthday and enjoy the sun, you've earned it."
Nina, who is currently on maternity leave, shares her baby daughter with her caterer husband, Ted.
Nancy's arrival was first announced on BBC Breakfast back in July by Nina's co-stars Jon Kay and Sally Nugent. Watch the sweet moment in the video below…
Since then, the news reporter has been incredibly open and honest about her postpartum journey which saw her grapple with swollen scars, hormonal crashes and exhaustion.
After admitting that her third pregnancy had been "harder" and was followed by a "tougher" delivery and "longer" recovery, Nina nonetheless assured her followers that she was "on the right track" and enjoying "life in the slow lane".
In addition to Nancy, the loved-up couple are also doting parents to their two boys: Digby, who arrived in 2016, and Michael, who was born two years later in 2018.
The duo have been together since 2013 after first meeting at a music festival in Croatia. They went on to tie the knot the following year in 2014.
On her big day, which saw the couple elope to New York, Nina looked every inch the beautiful bride in a chic white dress complete with a rounded neckline and a fitted waistline.
For some added warmth, the TV presenter wore a brown fur coat layered over her shoulders, whilst in her hands, Nina could be seen clasping a bunch of stunning red roses.
A pair of sunglasses and a gold clutch bag finished her low-key bridal look.