A British couple are to become parents of two sets of twin babies carried by two Indian surrogate women they have never met. Experts say twiblings - or children born to separate surrogates but created from the same batch of embryos - are not uncommon in India.
The four babies, all due in March 2014, are the result of a commercial surrogacy agreement with a clinic in the Indian city of Mumbai.
The husband, aged 35 and wife, aged 36, who do not want to be identified, travelled to India in May following two miscarriages and several failed attempts at fertility treatment in the UK.
"I thought to myself why wait and why waste any time and go through ups and downs and attempts again. We've had a long ten-year journey with this," he says.
There are no official figures, but Natalie Gamble, a lawyer who specialises in international surrogacy cases, estimates hundreds of British couples travel to India for surrogacy each year.
At the Corion clinic in Mumbai, the couple's eggs and sperm were fertilised to create embryos, which were then implanted in two different surrogates to increase the chances of a pregnancy.
"We had six embryos in the fridge and typically you would use one surrogate, but I thought get me two surrogates and implant three in each," says the husband.
A month later the clinic called with the news that one of the surrogates was pregnant with twins. They were both overjoyed.
Days later there was another call from the clinic.
"They found two heartbeats in the second surrogate," says the wife.
"The clinic was panicking because it's never happened before," she says.
"They asked us - is this what you want? Otherwise tell us now and we'll do the necessary."
However, the couple say there was never any question of terminating any of the pregnancies.
"Absolutely not, if there were three in each we would have had them."
In a few months' time they hope to return to India to pick up their four babies. They will not disclose how much they have paid the clinic, however, a surrogacy package in India, on average costs from £17,000 ($27,500) to £20,000 ($32,500).
They are grateful to the two women carrying their babies, but insist they have no intention of meeting either surrogate.
"She's doing a job for us, how often do you communicate with your builder or your gardener?"
"She'll get paid…we don't need to see her. As long as she's healthy and delivers my babies healthily, she's done a job for us," says the wife.
Neither is daunted by the challenge of having four babies and both are confident they will be able to financially provide for them.
For the professional couple from Bedfordshire, it is nothing short of an "amazing miracle".
"For me to have four children, it's going to be the same challenge as the next person having one child. I don't know any different, I'm over the moon, I can't wait," says the woman.
However, the case has raised concerns among health professionals in Britain. "It is troubling," says Dr Rima Rajkhowa, a consultant gynaecologist at Birmingham Women's Hospital.
"I think patients who don't work in the medical field are not aware of all the risks that are involved with multiple pregnancies. All they can think of and are focused on is having a child and they want to make sure every step is taken to get to that goal."
"I don't think any clinic in the UK will consider treating a commissioning couple with two surrogates simultaneously."
It is a view shared by lawyer Natalie Gamble.
"It wouldn't be allowed here. Under the regulation of licensed fertility clinics, there are quite strict rules about how many embryos can be transferred and certainly you couldn't transfer embryos to two surrogates in the same cycle," she says.
The UK's regulator, the Human Fertilisation and Embryology Authority (HFEA), says that multiple pregnancy can increase the risk of stillbirth, neonatal death and disability for the child and complications for the mother including late miscarriage, high blood pressure and pre-eclampsia.
They recommend single embryo transfer always be performed, unless there is a medical reason to transfer more than one embryo.
But how common is it for fertility clinics in India - a country where there are no laws governing surrogacy - to offer patients two or more surrogates at a time?
Dr Kaushal Kadam, medical director of the Corion clinic, which treated the British couple now expecting four babies, insists it is not common practice.
"It's usually a single surrogate but there are times when the couple want more," she says.
But is it really that unusual? Several couples who have had babies as a result of surrogacy in India have said clinics offered them the opportunity of using more than one surrogate per cycle.
Lawyer Natalie Gamble confirms there are similar cases but she believes it is a trend which is largely unique to the sub-continent.
"We've seen it a few times. I wouldn't say it's routine but it's not massively uncommon in India," she says.
In fact there is even a new term coined for these babies - twiblings.
"They're not quite twins and not quite siblings either," she says.
Medical experts believe twiblings represent a fertility phenomenon which has emerged as a direct result of India's estimated billion dollar surrogacy industry, an industry which critics say is driven by profit.
Surrogacy in the UK is a legal and ethical minefield. There are strict laws governing it and commercial surrogacy is banned.
Meanwhile, the Indian government is under increasing pressure to introduce laws to regulate the surrogacy industry.