It has paved the way for Vunipola to start at the Stadio Olimpico, while London Wasps loose-head prop Matt Mullan takes his place on the bench.
England are still in the hunt for their first RBS 6 Nations since 2011 and head coach Stuart Lancaster insists Vunipola will make a smooth transition back into the starting XV.
"It is important that Joe is with his partner at this exciting time," he said. "Family must always come first and everyone in the squad wishes them well.
"We have prepared for being without Joe and we have no doubt Mako will slot straight in and perform, as will Matt Mullan from the bench should he get an opportunity."