A set of octuplets has been born in California, a decade after a Nigerian woman became the first to deliver eight living babies into the world.
How rare is this?
Very rare indeed. There are just a handful of recorded cases involving eight or even nine babies, and there are no such sets where all have survived.
The largest multiple birth we know about was nonuplets in Australia in 1971 - all died within six days.
There are serious risks associated with multiple births
A Turkish woman lost her eight babies in 1985, a British woman hers in 1996.
The first octuplets to survive were born in 1998 - one died a week later but the other seven are now healthy 10-year-olds.
If all these babies born in California survive, they will be the first to do so.
How does it happen?
It is very unusual for such pregnancies to occur naturally.
Pregnancies involving large numbers of babies are usually the result of fertility drugs aimed at stimulating the number of eggs a woman releases.
Women are usually closely monitored to ensure too many eggs are not produced: if they are, she is generally advised to abstain from sex or use contraception to avoid the possibility of multiple births.
In this latest case, it appears the mother conceived her children through in vitro fertilization.
This has sparked a heated debate in the US about regulation surrounding IVF and the number of embryos which may be implanted at one time.
What are the dangers?
Multiple births are risky for both mother and babies.
A woman who is found to be carrying more than four foetuses tends to be advised to reduce that number in countries where abortion is legal.
This is to give at least some of the babies the best chance of survival in a cramped uterus.
In the UK, a woman called Mandy Allwood became the subject of a fierce medical and ethical debate after refusing what is known as a "selective" abortion.
She went on to lose all eight of her babies.
For the mother, there is a high risk of a raised blood pressure condition known as pre-eclampsia, which can be fatal if untreated.
She is also at a much higher risk of gestational diabetes - another condition which can prove very serious if not properly managed.
But these babies have been born, so what next?
The fact that the California babies have been born fairly late on in the pregnancy and appear to be a relatively healthy weight bodes well for them, according to Tim Overton, a foetal medicine expert from the Royal College of Obstetricians and Gynaecologists.
Mandy Allwood refused to abort any of her eight fetuses
"Based on what we know, the outlook appears pretty good for them.
"The big issues for the next few days will be respiratory problems as a result of under-developed lungs, and feeding problems, as premature babies are not always able to tolerate being fed outside of the womb.
"But with the close monitoring they will be getting, I would be cautiously optimistic."
Cerebral palsy - which affects movement - is the major concern for multiple birth babies.
For a woman carrying triplets, the risk of giving birth to a child with the condition is 47 times higher than if she was carrying a single child.
The symptoms of cerebral palsy - which can range from problems with balance to difficulty speaking - may take some time to manifest themselves.
And the long term?
If cerebral palsy does not affect these babies there is nothing to suggest they will not go on to live a life as healthy as that of a baby born without having shared a womb with seven brothers and sisters.