The KykNET star joked he advertised his children on Gumtree but admitted he did not receive any hits.
Adams and Gildenhuys are excited about the baby and say the other children are also excited about the prospect of another baby sister or brother.
Adams says they recently heard the good news and initially only told family and loved ones - but the secret is out now.
Gildenhuys is expected to give birth in June next year.
The couple have been together for 10 years and earlier this year celebrated their third wedding anniversary.
In April, Adams turned 40. The family celebrated with a trip to Thailand.
To crown it all, Adams marked 30 years in the entertainment industry.
He made his stage debut at the age of nine.
The couple’s youngest son, Malik, turned one in March and their first-born, Kadar Zayn is now three.
Gildenhuys said that even though they always wanted a “big” family, the thought of another “man” in the house was daunting. She is hoping for a girl.
Gildenhuys was a Miss South Africa finalist in 2008.
Adams admitted that at one stage he had to ask himself, “do I want to make more money or do I want to create more memories?”
The couple says the secret to their balanced family life is three months of hard work followed by a month of family time.