The couple also announced they were expecting their third child in December 2020.
Mike shared the happy news on his podcast, The Good, The Bad & The Rugby, and revealed the couple had just had their 12 week scan.
While they do stay quiet on many aspects of their private life, the royals have previously spoken about parenting.
During an appearance on Good Morning Britain in August 2020, Mike discussed the coronavirus lockdown with his daughters.
He said: “You get to watch her grow and change. You get stressed but at the majority of the time it’s with love.”
When the family have appeared out together, parenting experience manager at nursery Abacus Ark Jo Pandolfi, commented on Zara and Mike’s parenting.
The expert claimed Zara and Mike could use gentle competition to boost the confidence of the young royals.
Jo stated: “Zara and Mike Tindall want their daughters to be very competitive and Mike apparently beat his seven-year-old when teaching her to surf.
As well as encouraging the confidence of their children, the techniques may help the young royals become better at embracing changes.
The expert commented: “They are then far more likely to embrace new challenges as they grow and develop and will have better self-esteem.”
Zara and Mike have not announced the due date of their latest addition yet.
However, based on when their 12 week scan was, it is believed they are expecting in the spring months.
The royal line of succession – who outranks who?
The line of succession to the British throne dictates the order in which each member of the Royal Family would ascend to the throne.
It is also seen as a ranking of importance with the head of the line, the Queen, taking the place of ruler.
Older children come before younger children. Traditionally boys came before girls, but this law was changed on 26 March 2015 before the birth of Prince William’s first child.
Incredibly, Catholics are still excluded from the line of succession, as are children born outside of wedlock.
The royals, who usually stick to a strict protocol when appearing in public, often arrive at events in ascending order of importance, with the most important royal arriving last.
Prince Charles, 72, is currently first-in-line to the British throne, followed by Prince William, 38, his oldest son.
Then comes Prince William’s children, George, seven, Charlotte, five, and Louis, two, and they are followed by Prince Harry, 36. Prince Harry is succeeded by his son Archie Harrison, born in May 2019.