It could have been possible Rosalie was undetectable to begin with – sometimes a twin can’t be detected with an ultrasound because they are behind the other baby, it is so early in the pregnancy or simply due to human error.
But Rebecca said doctors concluded a rare superfetation event had happened, partly because Rosalie was smaller but still growing at a healthy rate.
Rebecca said: “I didn’t even know that existed. Even my midwife found it baffling.
“It was a massive shock finding out about the twins so we waited until they were born to find out about their gender.”
Rebecca had her twins at the Royal United Hospital in Bath on the same day, despite being conceived three weeks apart.
A problem with Rosalie’s umbilical cord meant the twins had to be delivered sooner than planned, when Noah was 33 weeks.
Rebecca gave birth to Noah, 4lb 10oz and Rosalie 2lb 7oz via C-section on the 17th of September with Rhys by her side.
Rosalie was transported to St Michael’s Hospital in Bristol for 95 days where she was cared for in intensive care.
Rebecca said: “It was such a relief as we were always worried that something terrible would happen to Rosalie as she was so much smaller.
“I was really really nervous during the birth but when they were born they showed them too which was amazing.
“After they sewed me up they took to me to NICU to see them which was lovely.
“They were just beautiful, especially Rosalie she was so small her nappy came up to her armpits.”
Noah remained in Bath for three weeks and three days before going home to meet his 14-year-old sister Summer.
Rebecca said: “We feel really lucky, it’s so lucky to have twins anyway but to have such special twins, it’s so lovely, it’s wonderful, they are a blessing.”
Loving mum Rebecca documents their progress at home on her Instgram @roberts.supertwins.
She said: “It was amazing to finally have them all home.