In 2020, 39-year-old clothing designer Rebecca Roberts and her partner Rhys Weaver, 43, were stunned during an ultrasound of their 12-week-old baby boy, Noah. To their surprise, they discovered he wasn’t alone—he had a companion, leading to the later birth of their daughter, Rosalie. Despite doctors warning that the second baby might not survive, Roberts remained hopeful. The two babies were conceived three weeks apart at Royal United Hospital in Bath. Noah was born on August 25, 2020, weighing 4 lbs 10 oz, while Rosalie arrived on September 17, 2020, weighing 2 lbs 7 oz. This rare phenomenon, called superfetation, occurs when a pregnant woman conceives a second child during an ongoing pregnancy.
Reflecting on the experience, Roberts said, “We feel really lucky. It’s special to have twins, but to have such unique twins is wonderful—they are a blessing.”
When doctors suggested it was a case of superfetation, Roberts was taken aback by the rarity of her pregnancy. “I didn’t even know that was possible. Even my midwife found it baffling,” she shared.
Noah and RosalieDue to her tiny size, Rosalie was transferred to the larger St. Michael’s Hospital in Bristol, where she spent 95 days gaining strength.
Meanwhile, Noah was healthy enough to remain in Bath, though he required three weeks of hospital care before going home to meet his 14-year-old sister, Summer.
Rebecca isn’t the only woman to recently make headlines for becoming pregnant while already expecting.
“Medically, it’s considered an anomaly,” explains Dr. Misra-Sharp. “It’s important to differentiate superfetation from more common conditions like twinning, whether fraternal or identical, as they are often confused.”
“The key difference is that superfetation involves eggs being released and fertilized at different times, often weeks apart, while twins are the result of eggs fertilized simultaneously,” the doctor clarifies.
Superfetation can typically be detected through prenatal ultrasounds, as scans will show the two fetuses at different stages of development.
“One fetus will appear noticeably smaller or younger than the other, often by a few weeks,” she adds. “In twinning, even if there are size differences, the fetuses are the same gestational age, with any disparities usually attributed to growth issues.”
