A prominent Waterbury gynecologist was fined $5,000 by the state Medical Examining Board Tuesday for mistakenly performing a laparoscopic hysterectomy on a patient who he did not know was pregnant, state records show. In January 2011, Dr. Jonathan Foster, who is also an obstetrician, failed to detect the patient’s pregnancy before the operation, according to a consent order he signed in July agreeing to the punishment. He also relied on the patient’s statement that she was not pregnant and failed to follow-up a urine pregnancy test with a blood test or ultrasound before operating, the order said. State records do not indicate how far along the pregnancy was. After the incident, Foster completed a course to maintain his certification in his specialty.