On Wednesday Travolta, 56, wrote on his website that his wife Preston, 47, was three months pregnant.
Travolta wrote: "It's impossible to keep a secret... especially one as wonderful as this."
The couple already have a 10 year old daughter, Ella and are still trying to come to terms with the death of their 16-year-old son Jett last year.
Jett died of a seizure last January in the Bahamas.
He suffered from rare Kawasaki disease.
Tragedy seems to follow the Travoltas.
Last week their two dogs were killed by an airport truck in Maine.
The pregnancy has been called "a miracle" because of Kelly's age.
She is due in November.