While Mr Joyce has experienced parenting before, being a father to four children with his wife Natalie, this is the first baby for Ms Campion.
The new addition will Joyce's elder children, four girls named Julia, Caroline, Odette and Bridgette.
Joyce is technically still married but separated from his first wife, Natalie – however, he is reportedly in a "happy" relationship with his former staffer Vikki Champion.
The two politicians caused controversy last year when it was confirmed that they allegedly had an affair together.
Mr Joyce was axed from his cabinet position and the Nationals leadership after as a result of his relationship with Ms Campion came public and news broke that the two were expecting a child.
Following this scandal, Prime Minister Malcolm Turnbull created a ban on ministers partaking in sexual relations with their staff.
Joyce has stayed on as the member for New England on the back bench.
While Mr Joyce has resigned, he made a public statement, pleading with media outlets to stop targetting his family, as an attempt to save his unborn son, his four daughters, and estranged wife any more pain.
“This has got to stop. It’s not fair on them,” he said.
“I won’t snipe. I have a lot of things I need to do.
“I want to assist my colleagues where I can to keep their seats and also, quite naturally, in April, a baby will be born.
“I’ll have other things on my mind.”