In a post to his public social media pages, Bishop shared a photo of Raeburn, their pets and himself holding a photo of an ultrasound.
Many of his followers took the opportunity to congratulate the couple including fellow National MP Simeon Brown and Labour MP Barbara Edmonds.
In January Bishop told the Herald he was nervous but excited about becoming a dad and said he was aware his life would change significantly with the arrival of his son.
He also said National Party leader Christopher Luxon was one of the first MPs he told about the baby.
"He seemed even more excited than I was, fatherhood is really important to him and family is important," Bishop said, adding that Luxon had encouraged him to take as much time off as he needed.
In January he said he would be taking paternity leave when his son arrived, which also happens to coincide with a three-week parliamentary recess.
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