The Jerry Maguire star talked about the 16 year old's struggle with autism during a segment taped for U.S. series Doctors, and admitted she and husband John Travolta blamed several factors for his condition.
She says, "(Jett) was autistic. He had seizures and when he was very young, he had Kawasaki syndrome (an autoimmune disease). I strongly believe as a mother, as does my husband, that there are certain contributing factors that lead to autism and some of it is very much the chemicals in our environment and in our food."
Jett suffered a fatal seizure after hitting his head in a bathtub while on a family vacation in the Bahamas, and Preston believes autism contributed to the tragedy.
She fears complications from her "fast and hard" labour and taking antibiotics while breast feeding may have caused him to develop autism.
Preston's episode of Doctors airs in the U.S. on Wednesday (21Nov12).