Doctors realized that something was up during an ultrasound when they looked at the screen and noticed that one fetus still looked like a blob, whereas the other had four visible limbs. It was such a marked difference.

“It was really strange to see. The doctor said that he had never seen it before, but had only read about it in textbooks.

“One foetus was 12 weeks old, whilst they said the other was three weeks behind, at nine weeks old. I had become pregnant twice on two separate occasions.

“The doctors couldn’t believe it, either. They told us there was a million-to-one chance of it happening.

“There were concerns for the smaller baby but at the next scan she was still alive.

Miss Spence said: “It was very emotional when the doctors said that the smaller baby was still growing. She was such a little fighter.”

The mother had to be scanned every week to check that both babies were still growing.

She said: “It was nerve-racking going to the hospital each week and I just kept praying they would both be all right. My stomach got so big that towards the end of my pregnancy, I could hardly move.”

Doctors had to carry out an emergency caesarean to deliver the babies because they were both lying awkwardly in the womb.

Ame, the younger baby, arrived first weighing 4lb 13oz. Her sister Lia was much bigger at 6lb 11oz.

This may not be too uncommon because there are statistics on twins that are born to two fathers, which is kind of the same thing because the female would release an egg at 2 different times.

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