Giving birth to twins, the mother was shocked to learn the truth, there were only 10 cases in human history.

That is a rare story that happened to a woman named Sophie Small (30 years old), a swimming coach in Leominster town, Herefordshire county (England).

In August 2020, Sophie gave birth to two beautiful girls, Holly and Darcy . Throughout her pregnancy, the mother still thought she was pregnant with twins. However, when the two children cried out at birth, both the doctor and the midwives were surprised by their weight. Darcy came first and weighed only 1.9 kg, while Holly, the baby born later, weighed 2.75 kg.

Sophie Small gave birth to daughters Holly and Darcy in August 2020. She initially believed the girls were twins.

From here, the truth gradually became clear. After investigation, doctors determined that the girls were actually conceived 1 month apart . That is, while pregnant with Holly, Sophie continued to ovulate and conceived baby Darcy.

Sophie Small's husband Jonathan poses with his newborn daughters.

This is called "superfetation" - an extremely rare phenomenon in which a pregnant woman becomes pregnant with another baby while she is already pregnant.

According to the Cleveland Clinic, the phenomenon of "Superfetation" is very rare in humans. There have only been about 10 confirmed cases in human history.

The clinic's website says: 'It is so strange and rare that when it happens it often causes a stir. In general, the probability of Superfetation occurring is almost zero . '

The two children are the result of a rare phenomenon.

The clinic claims that a pregnant woman's body will undergo 'hormonal changes that make further pregnancy almost impossible while the egg has been fertilised and the embryo has developed inside the uterus'.

For her part, Sophie told Kennedy News that her pregnancy was 'horrible'. She suffered from severe morning sickness and was hospitalized eight times in seven weeks.

Sophie Small's twin daughters.

The mother said: 'I was pregnant with two babies who were at different stages of development but my husband and I had no idea. The doctors didn't know either. They couldn't figure out why I was pregnant with twins in such a strange way. I was expecting twins but one was bigger than the other.'

She added: 'They had their own sacs and placentas. But doctors couldn't figure out why one was so advanced.' It was only after tests were carried out that doctors determined that the babies were not twins at all.

The two sisters were born with very different weights.

'Darcy was born at 32 weeks and Holly was in the womb for 36 weeks ,' Sophie said.

Many people didn't believe Sophie when she told them the unbelievable story that happened to her. 'People thought I was crazy when I explained the differences between my two daughters ,' Sophie said.

Meanwhile, others do not even believe that the two girls are related due to their different appearances and personalities.

'Holly has blonde hair, big beautiful blue eyes and wants to be a princess or a jockey,' the mother explained.  'Darcy's hair is mouse brown, she's a tomboy and wants to be a train conductor when she grows up.'

Sadly, Holly was born with cerebral palsy , which affects the right side of her body, and doctors are still unsure whether the condition is the result of a rare phenomenon called "Superfetation" .

Meanwhile, Darcy's stomach lining was not fully developed at the time of birth , as she was born prematurely at 32 weeks.

Sophie told Kennedy News that her daughters spent the first few months of their lives in hospital but are now thriving.

'They are playful, happy children and are absolutely thriving. They have recently started nursery and are very confident.'

'I don't know what the future holds. It's been tough but we're so happy and lucky to have our children ,' Sophie said.