Millie Radford turned 19 today.

The teen, who is part of Britain’s biggest family, celebrated the occasion while heavily pregnant.

Her mum Sue, who has 21 other children, marked the event with a sweet Instagram post.

She posted several photos of Millie, including one taken in Orlando, Florida, during a family holiday.

The Radfords matriarch wrote: “Massive happy birthday to @millieeradfordd – 19 today.

“Have a brilliant day sweetheart. #BirthdayGirl #19Today.”

Sue Radford shared this sweet throwback picture of Millie and two of her sisters in Orlando, Florida

Sue’s post has racked up 3,400 likes in less than an hour.

Many took the time to leave birthday messages for Millie, with one responder gushing: “Hope you have a fantastic day”.

Another said: “Happy 19th babe. Have a great day.”

A third remarked: “Happy birthday gorgeous girl!”

And a fourth added: “Happy birthday Millie. Put your feet up and enjoy our special day.”

Millie is currently pregnant – and her due date is in September

Millie’s 19th birthday looks very different to the one she had last year.

This is because the teen is currently pregnant with her first child.

Her little girl, Ophelia, is due in just a few weeks after being conceived during a six month relationship with an unknown partner.

While Millie and her baby’s father have now split, it seems she’s more than prepared for the arrival of her daughter.

Posting on Instagram, where she had 72,300 followers, Millie shared a snap sitting in her new nursery.

Millie has prepared well for baby Ophelia's arrival

The mum-to-be captioned the post with a checklist.

She ticked off all the baby goodies she had, including a pram, car seat, hospital bag and coming home outfit.

Millie broke down in tears last month as her parents gifted her an Egg pram, carry cot and nappy bag. The set cost over £1,100.

She also proudly showed off her baby's new room recently.