Difficulty concentrating can be due to many processes of pregnancy. Decreased sleep is the most common cause, but if difficulty concentrating occurs with confusion and elevated blood pressure, you may have a life-threatening condition and should contact your physician immediately. There are reports of "pregnancy brain" referring to a fog, difficulty concentrating, and difficulty remembering things. Unfortunately, there have been no surveys of frequency or studies about pregnancy brains. Currently, the literature has no concrete evidence suggestive of a cause, but common theories include a shift in hormones, blood flow, lack of sleep, or general stress as contributors to pregnancy-associated confusion.