The 40-year-old and Martin have been married for almost a decade. Paltrow says that cases of infidelity can raise questions on an individual's existence, reports femalefirst.co.uk.
"I think it would be hard for me to be one of those wives who finds out there's been something going on behind my back 20 years in. I'd imagine you'd begin to question your life," said Paltrow.
"It would definitely make things harder but I believe that if there's authenticity and honesty right off the bat things will be okay," she added.
The actress believes that every couple faced different kinds of challenges.
"I think that if the idea of being committed to someone is important to you, you begin to value certain parts of your social life over another. No couple is the same, and as such, every couple takes on different challenges," Paltrow said.
"I would like to think that I would be forgiving or forgiven, but I can't give an honest answer as I haven't really experienced that," she added.