From a story on psycom.net by  Holly Pevzner headlined “9 Signs You’re Married to a Narcissist—and What  to Do About It”:

It’s not that there are no red flags that signal narcissism during dating, it’s that many of the tell-tale traits of narcissism become more pronounced after getting hitched. “With marriage—and parenthood—there’s more interdependence, more demands,” says Ramani Durvasula, Ph.D., author of Should I Stay or Should I Go: How to Survive a Relationship with a Narcissist.