The parents of sextuplets were today said to be hoping for a "small miracle" as their babies were fighting for their lives in hospital.
The six - four girls and two boys - were born last Friday to Andy and Vicky Lamb, both 31, from Oxford.
Delivered 14 weeks early, a representative of the family said the tiny tots remained in a critical condition today. Their mother is said to be recovering well.
The six were born at the John Radcliffe Hospital in Oxford shortly after 11pm last Friday. Their birth weights ranged from 1lb 5oz (590g) to 1lb 15oz (885g), the hospital said.
Mrs Lamb fell pregnant after taking the same fertility drug she used before the pregnancy of her first child, Gracie, now aged five.
The family's representative Max Clifford said: "They are just incredibly grateful for the John Radcliffe Hospital, the doctors and the nurses."
Talking about when the couple might be able to take the six home, Mr Clifford said: "It is a long way off. They are fighting for their lives, they are still critical."
In an interview with GMTV, Mr Clifford added that Mr and Mrs Lamb were "hoping and praying that everything is going to be okay - but they realise they are praying for a small miracle".
The four girls and two boys are being monitored at the John Radcliffe's neonatal intensive care unit.
Live births of sextuplets are rare, occurring approximately once in every 4.5 million pregnancies.
According to the Multiple Births Foundation charity, the last surviving set of sextuplets in Britain were born in 1993.
The latest set were delivered by a large team of doctors and nurses following several weeks of planning.
Kenny McCormick, consultant neonatologist at the hospital, said: "The next few days and weeks will be critical. Babies that are born this early need a lot of specialist care.
"They are receiving round-the-clock intensive care and specialist nursing at the moment and their condition is constantly monitored."
Keith Reed, chief executive of the Twins and Multiple Births Association, said it was "truly amazing news".
He said: "We waited for decades for the birth of sextuplets in the UK and now two sets have now been born within the space of the year.
"Around half of the 11,000 multiple birth babies end up being cared for in a neonatal intensive care unit. Families in this situation face a rollercoaster of emotions and we all wish the whole Lamb family well."