Mother has rare ‘double pregnancy’ as she conceives daughter weeks after falling pregnant with son

With their strikingly different sizes, it is hard to believe these babies are twins.

But that is because they are medical wonders – after being conceived three weeks apart.

In an incredibly rare phenomenon known as superfetation, Rebecca Roberts effectively got pregnant with Rosalie while already pregnant with Noah.

Only about a dozen such cases are documented worldwide.

Miss Roberts, 39, was stunned when she found out she was having twins as two earlier scans showed no hint of a second foetus.

She said: ‘I didn’t even know it was possible to conceive again while pregnant.’

Rebecca Roberts, 39, (right) was stunned when she learned she was pregnant with twins as earlier scans only showed one foetus but an incredibly rare phenomenon known as superfetation meant she got pregnant with Rosalie (centre) while already carrying Noah (left)

The twins were delivered early by caesarean at 33 weeks last September due to a problem with Rosalie’s umbilical cord.

It meant while Noah weighed 4lb 10oz, his sister was just 2lb 7oz.

Rosalie was finally discharged home to Trowbridge, Wiltshire, at Christmas, two-and-a-half months after her twin.

She was 71b 4oz last week when the midwife visited. Some experts are sceptical that superfetation exists.

The twins (pictured left) were delivered by caesarean at 33 weeks last September which meant while Noah weighed 4lb 10oz, his sister was just 2lb 7oz and had to stay in hospital for two and a half months. Pictured: Rosalie’s hand next to her father’s finger after she was born (right)

But Miss Roberts, who runs a children’s clothing firm and also has daughter Summer, 14, had tests to rule out chromosomal or genetic reasons.

She and partner Rhys Weaver, 43, have been told a fertility drug she was taking may have caused her to release an egg while already pregnant.

*follow the twins’ progress on Instagram at: roberts.supertwins