What to Expect When You're Expecting is a pregnancy guide, now in its fourth edition, written by Heidi Murkoff and Sharon Mazel and published by Workman Publishing. Originally published in 1984, the book consistently tops The New York Times Best Seller list in the paperback advice category, is one of USA Todays "25 Most Influential Books" of the past 25 years and has been described as "the bible of American pregnancy". , over 14.5 million copies were in print. According to USA Today, 93 percent of all expectant mothers who read a pregnancy guide read What to Expect When You're Expecting. In 2012, What to Expect When You're Expecting was adapted into a film released by Lionsgate.