'I got pregnant while I was already three weeks pregnant and now have twins'

A woman who got pregnant while already three weeks pregnant has given birth to healthy twins in an extremely rare phenomenon.

Rebecca Robertson found out she was having twins, but was shocked when she was told that one was smaller than the other.

Exactly three weeks smaller.

There have been just 13 other documented cases of superfetation in the world before little Noah and Rosalie were born in September last year.

Speaking to the Mirror, Rebecca said her pregnancy was a rollercoaster of emotions as she felt doctors were almost trying to prove there was something wrong with the smaller twin, as superfetation is so unusual.

The mum-of-three said she and partner Rhys Weaver found out they were having a baby back in February last year, before the UK's first coronavirus lockdown.

The 39-year-old said: "I was offered an early scan at seven weeks, Rhys was able to come to the scan too as hospitals were still open at that point. We saw our tiny, little baby, just. It was so small and we were told we were expecting one baby.

"Fast forward a few weeks and I had my 12 week scan. Unfortunately Rhys wasn’t allowed in the hospital as lockdown had begun."

Rebecca from Trowbridge, Wiltshire, was told she was expecting twins, but added that things suddenly got "even more amazing".

She said: "It was very obvious that one twin was much bigger than the other. There was a three week size difference between them both.

"They could not understand what was going on and why the size difference was so big.

"After multiple scans, the twin specialist at Bath Royal United Hospital came to the conclusion that I had ovulated again. So basically I got pregnant whilst being pregnant."

The couple were shocked by the news and Rebecca admitted she went home to " Google " superfetation.

"We were told it was very, very rare, but we found out there were only a handful of other stories, there are just 13 documented cases in the world ever."

Rebecca, who already has 14-year-old daughter Summer from a previous relationship, said the pregnancy became a troubling time as some doctors were convinced their diagnosis of superfetation was unlikely.

They were worried that the smaller baby had something wrong or was not developing correctly, maybe it had caught a virus or had a chromosome problem.

Rebecca said: "It was like they were trying to prove that something was wrong, they were adamant it wasn't superfetation.

"Our world came crashing down, I couldn't enjoy my pregnancy at all, all the things you are supposed to enjoy were gone.

"It was very, very scary. It was a long time of upsets and constant lows.

"When we were told by a doctor that she didn't think it was superfetation, that massively knocked us for six.

"It was heartbreaking."

She added: "To us, when they said superfetation it made sense. You could see Rosalie - or twin two as she was then - you could see she was smaller.

"The smaller baby always remained three weeks smaller than the bigger one, it was consistent."

In September, doctors noticed there was an issue with twin two's umbilical cord, so Rebecca was taken in for a C-section at 33 weeks.

The twins were born on September 17. Noah was born weighing 2kg (4lbs 10z) and Rosalie was 1.1kg (2lbs 7oz).

The babies spent the first two and a half weeks of their lives apart as Noah stayed at Bath Hospital and Rosalie was whisked off to special care in Bristol, with their mum and dad having to split time between their two new babies in separate cities.

Two weeks later little Rosalie was transferred back to Bath NICU to be reunited with her brother Noah.

Noah spent three weeks and three days in neonatal intensive care, and Rosalie spent 95 days there before being finally allowed to go home in the days before Christmas.

Their parents avoided telling friends and their wider family about their births until recently, when they finally felt confident that the babies were fine.

Rebecca is now documenting her superfetation twins on her Instagram page roberts.supertwins where she shares images and updates about them.

She added: "We were too scared to say anything, we told our close family and we were very careful just because we were scared if anything happened, but something good did come out of 2020.

"It's the most strangest, amazing, miracle and it happened to us. I do feel very lucky.

"A friend said Rosalie is meant to be in this world, she fought all the way to be here."