A woman has given birth to eight babies in five minutes - with the last of the octuplets a total surprise to the mother and medical team despite months of planning.
The six boys and two girls were delivered 'kicking and screaming' and are all said to be doing well. Doctors warned today that the next 72 hours will be critical.
But there are good signs already. Each baby cried spontaneously after the birth - and although two initially had to be on ventilators, they are now breathing on their own.
It is only the second time that eight babies have been born alive in the United States and survived more than a few hours.
Preliminary research into worldwide survival rates for octuplets showed the majority dying within hours - meaning if these newborns survive the next 24 hours, they may be the world's first set to do so.
The mother's identity is being kept secret - but, her doctors said, she is 'very strong'. She checked into the hospital at 23 weeks, and stayed there for seven weeks until the babies were born.
Doctors at the hospital in the town of Bellflower near Los Angeles told of their delight at the smooth delivery of babies they called A, B, C, D, E, F and G as they arrived - and their surprise when the eighth, Baby H, was born.
The babies weighed between 1lb 8oz and 3lb 4oz and were delivered between 10.43am and 10.48am local time yesterday, doctors at Kaiser Permanante Bellflower Medical Center said.
Los Angeles is eight hours behind the UK - meaning the babies will have survived their first 24 hours at between 6.43 and 6.48pm UK time this evening.
Each baby was shown to the mother, who was awake during the Caesarean section, and then taken into another room while staff waited for the next to be born.
'My eyes were wide,' Dr. Karen Maples said, explaining her reaction to the last birth.
Doctors said the babies were born nine weeks premature but are in stable condition. Two newborns were initially placed on ventilators that have now been removed, and a third needs oxygen. All eight babies are likely remain in hospital for two months.
It is unclear whether the mother had became pregnant through fertility treatment, which can raise the likelihood of multiple births.
The mother plans to breastfeed all eight babies, her doctors said.
Forty-six hospital staff and four delivery rooms were used for the births.
But despite weeks of preparation, doctors did not expect the eighth child.
'It is quite easy to miss a baby when you're anticipating seven babies,' said Dr. Harold Henry, chief of maternal and fetal medicine at the hospital.
'Ultrasound doesn't show you everything.'
Maples said the babies would probably remain in the hospital for at least two months. She said the mother should be released in a week.
Kaiser spokeswoman Myra Suarez said she could not release any information about the mother, including her condition or whether she used fertility drugs.
Such drugs make multiple births more likely.
'They are all doing the best they can,' Suarez said.
The first baby was born at 10.43 am; the eighth one at 10.48 am.
'They were all screaming and kicking around very vigorously,' Dr Harold Henry said.
The octuplets are the second reported to have been live born in the U.S. The first live-born octuplets were born in Houston in 1998, and one baby died about a week later.
The surviving siblings - girls Ebuka, Gorom, Chidi, Chima and Echerem, and their brothers Ikem and Jioke - celebrated their 10th birthday in December.
Their Nigerian-born parents, Nkem Chukwu and Iyke Louis Udobi, said they are astonished and grateful that their children have grown up to be healthy and active kids who are now in the fourth grade.
Chukwu said that the parents of the newest octuplets have much to look forward to.
'Just enjoy it. It's a blessing, truly a blessing,' Chukwu said.
'We'll keep praying for them.'
In 1996, Briton Mandy Allwood underwent fertility treatment and became pregnant with eight foetuses.
The then 32-year-old, from Solihull, West Midlands, rejected medical advice to abort some of them.
All eight of her babies died.
The Bellflower medical centre is about 17 miles south-east of Los Angeles.