A Chinese woman has delivered a healthy boy from an embryo frozen for 10 years - a decade after the birth of her elder son conceived in the same round of IVF, according to a hospital.
The mother, 41-year-old Ms Wang, went to fertility specialists for help in 2009 after trying and failing to conceive for five years.
Doctors said they cultivated 'a batch of embryos' using the same sperm and eggs. One of them was implanted into her straight away, and the rest was frozen.
A hospital handout picture shows a doctor holding the baby after he was born in Hubei on June 16. The boy was conceived in the same round of IVF as his elder brother, who is 10 years old
The boy who was born from a decade-old frozen embryo weighed 3.48 kilograms at birth
Ms Wang's elder son, nicknamed Lu Lu, was born in June, 2010, at the Hubei Maternal and Child Healthcare Hospital in central China.
Her younger son, nicknamed Tong Tong, was born on Tuesday at the same hospital.
'From a medical perspective, Lu Lu and Tong Tong are twin brothers,' said Zheng Jie, a doctor from the hospital's fertility centre.
Dr Zheng did not give more details of the twins but said the pair weighed the same at birth at 3.48 kilograms (7.7 pounds).
The boy was born via a caesarean section at the Hubei Maternal and Child Healthcare Hospital
Social media footage posted by the hospital shows the boy crying out loud after being born
Ms Wang's case was revealed by the hospital in a social media post yesterday.
According to the hospital, Ms Wang resorted to IVF after experiencing repeated miscarriages.
Dr Zheng, who treated Ms Wang in 2009, discovered that she suffered from blocked fallopian tubes and suggested that she and her husband try for IVF.
Ms Wang said that although 'test-tube babies' were uncommon in China at the time, she decided to give it a go as 'the last straw'.
After Dr Zheng and her team successfully grew several embryos from the same batch of sperm and eggs, one of them was implanted into Ms Wang in October that year.
The baby was born the following June via a caesarean section.
Ms Wang said that she and her husband decided to have another child because their son, Lu Lu, kept asking them for a younger sister or brother.
The couple, therefore, went back to the same hospital and doctor to realise the wish.
The baby and his brother were conceived via IVF using the same batch of sperm and eggs. Their parents decided to try for another baby after their firstborn kept asking for a sibling
The hospital noted they had been honest with Ms Wang about her chances of success considering her age.
Medics thawed the frozen embryos from 10 years earlier, cultivated them in the lab for further two to three days and selected the one with of 'highest quality' to transfer into Ms Wang's womb, the team said.
Ms Wang gave birth to her younger child on June 16, also via a C-section.
Social media footage posted by the hospital shows the boy crying out loud after being born.
Medics can be heard saying: 'We finally meet after 10 years.'
Since the baby shared so many similarities with their first-born, the couple gave him the nickname Tong Tong, which means 'same same' in Chinese.
HOW CAN YOU HAVE CHILDREN FROM THE SAME IVF CYCLE?
Siblings can be born from the same IVF cycle years apart using embryo freezing.
Following IVF, many woman have good-quality embryos left over after one has been implanted into their womb.
Rather than discarding these embryos, they can be frozen for future use.
This can help to preserve a woman's fertility and is more effective than freezing your eggs.
The standard storage window for frozen embryos is ten years, however, women in 'exceptional circumstances' can store them for up to 55 years.
The average cost for storing them for a year is between £170 and £400.
When a woman wants to use her frozen embryos, they can be thawed and transferred into her womb.
This will only occur without fertility drugs if she is ovulating regularly.
If her periods are irregular, she may require medication to trigger a 'false' menstruation that prepares her uterus lining for an embryo.
Success rates for IVF using frozen embryos are on the rise and are now comparable to fresh embryo rates.
However, not all frozen embryos survive the process.
But it is as safe as 'normal' IVF, with the main risk being having twins or triplets.
If the frozen embryos are never needed, they can be discarded, or donated to another woman, research or training.
Source: Human Fertilisation & Embryology Authority