For the majority of families the birth of twin baby girls would be a happy occasion.
But for the Bichards, from Dundee, the arrival of Sarah and Rachel two decades ago led to a fraught and fearful few weeks full of unknowns.
The pair were born so prematurely they were among the smallest newborns ever delivered in Ninewells, and doctors did not believe they would survive.
But now, 21 years after defying the odds, the twins are gearing up to celebrate their birthday among friends and family.
Rachel said: “It’s crazy to think we are turning 21 – it only feels like yesterday it was our 18th birthday.
“We are having a big party at the end of the month with all the family, so we are looking forward to that.”
Following their birth the pair were put on ventilators and, when they were just a few weeks old, had to be taken to the Royal Hospital for Sick Children, in Edinburgh, where they had operations to close a heart duct.
They also had to undergo laser surgery for eye problems.
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Since coming through those trying times the pair have still had to monitor their health closely.
Sarah has had lasting effects from the difficult birth, and Rachel has had a colostomy bag fitted in recent years due to bowel problems.
But the pair are thankful that they overcame the odds all those years ago – Rachel works full time at Rainbow Bright Nursery, in Downfield, while Sarah is in her final year at Dundee College.
And knowing what their first few months in the world were like, the twins’ attitude is to take each day as it comes and make every moment count.
Rachel said: “I have been working full-time at a nursery and I am really enjoying it.
“I’m getting training on the job to become a nursery nurse, so that’s been really good.”
And the sisters aren’t going to wait until the end of the month to mark their milestone, as the celebrations begin in earnest tonight.
Rachel said: “We are going to the bingo as today is the day we actually turn 21. I’m going with my sister and our mum and granny, so that will be good fun. Hopefully we will win.”
Despite the celebrations, their mum Mandy said it had been tough for the family over the years, but they always tried to look at the positive side of life.
She said: “Since their 18th, Rachel has had to be fitted with a colostomy bag and we also worry about what Sarah is going to do when she leaves college.
“It has been tough, but we just have to keep laughing, because if you are happy then that is all that matters. The girls have been an inspiration to all of us.”
Mandy is also looking forward to the 21st birthday celebrations, although she said she hopes things don’t get too rowdy.
The Downfield resident said: “There are currently 170 people on the guest list for the party, but I am secretly hoping that number might come down a bit because that is a lot of people.
“The twins are like big kids really so they will enjoy the games and things at the party with their friends.
This year has proven to be full of milestones for the Bichard family as Mandy has also had a special birthday of her own.
She said: “I turned 50 this year and there were other special birthdays in the family too. I didn’t do anything for my birthday, though – after a certain age you tend to stop counting.”