Alisha, Anoushka, Ashley and Amelia Harrison are quadruplets with a difference.

They were born in pairs 19 months apart and are believed to be the UK's first test tube quads to be separated by a gap.

Maria Harrison, 30, had twins Alisha and Anoushka 19 months ago after in vitro fertilisation (IVF) treatment at Leeds General Infirmary.

Mrs Harrison and husband Duane, of Filey, North Yorkshire, then decided to try for more children and had another two fertilised eggs from the same batch implanted.

Eight weeks ago the second set of twins, Ashley and Amelia, were born.

Mrs Harrison, who had fertility treatment after trying for children for five years, said: "I suppose you can say we have two sets of twins but technically they are quads.

"It's all very confusing.

'Wonderful bonus'

"We were overjoyed the first time but the second babies were a wonderful bonus we could never really have hoped for."

She added: "People talk about the miracles of modern science and the children are living examples.

"Words can't describe how lucky my husband and I feel."

Couples who have IVF treatment have a one-in-four chance of having a baby, with a quarter of the births being twins.

Doctors say it is extremely rare for IVF mothers to have twins twice.