United Artists has optioned Elaine Kagan’s upcoming novel “Somebody’s Baby” for producer Frank Mancuso Jr.’s FGM Entertainment, the studio confirmed Wednesday.If the film gets made, the deal could be worth in the mid-six figures for Kagan, who previously wrote the novels “The Girls” and “Blue Heaven.” Described as an American “Secrets & Lies,” story follows star-crossed lovers — a teenage girl from an upper-crust family and a handsome but older blue-collar worker — whose out-of-wedlock affair leaves the young woman pregnant. When the man doesn’t show on the night they’re planning to elope, the girl gives up the baby for adoption. Thirty years later, the grown child seeks her biological family, reunites her parents and discovers the truth behind their failed relationship. Morrow is slated to publish the book in May. Marjorie Lewis, exec VP of development at FGM, brought the project into the production company. Kagan also is an actress whose credits include roles in “Absolute Power,” “Beverly Hills Cop III,” “Angie,” “Goodfellas” and “Coming to America.” She began her career working in production for John Cassavetes. Bill Contardi and Amy Schiffman of the William Morris Agency brokered Kagan’s deal on behalf of her Gotham lit agent, Ginger Barber.