Jessica Allen was acting as a surrogate for a Chinese couple when at a six-week ultrasound, she discovered she was carrying twins. They naturally assumed the transplanted embryo had split.
It wasn’t until a month after the babies were born via caesarian that they discovered one of the babies was her biological son. The adoptive couple were preparing to return home to China when Jessica and her husband, Wardell, received a text message and photograph from the mother, stating that the “twins” had different skin tones.
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DNA tests eventually determined that the baby was Jessica and Wardell’s but it took another month of fighting to get custody of him.
"I don't know how to describe it ... we were floored," Jessica told ABC news. "We were like, how did this happen?"
It turns out that Jessica had experienced superfetation, when a woman continues to ovulate while pregnant, which allows a second egg to fertilise and implant itself in the the womb. Their son, Malachi, was actually three weeks younger than the surrogate child.
Dr. Jennifer Ashton told ABC that this is an incredibly occurrence with no known explanation.