On October 22, 2005, about 1440 eastern daylight time, a Boeing 737-832, N378DA, operated by Delta Air Lines Inc., as flight 612, was not damaged during an encounter with turbulence in cruise flight about 300 miles northwest of Hamilton, Bermuda. There were no injuries to the 2 certificated airline transport pilots, 2 flight attendants, and 143 passengers; while 1 flight attendant was seriously injured, and 2 passengers sustained minor injuries. Visual meteorological conditions prevailed for the flight that departed Hamilton, Bermuda; destined for General Edward Lawrence Logan International Airport (BOS), Boston, Massachusetts. An instrument flight rules flight plan was filed for the air carrier flight conducted under 14 CFR Part 121. The flightcrew reported that light turbulence prevailed during the climb from Bermuda, and the seatbelt sign remained illuminated. About 230 miles northwest of Bermuda, at 34,000 feet, the turbulence subsided; however, more turbulence was forecasted for about 150 miles ahead of the airplane. The captain announced to the passengers that the seatbelt sign would be turned off for 10 minutes to allow them an opportunity to move about the cabin, but would be turned on again due to the upcoming turbulence. The captain also decided against meal service due to the anticipated turbulence after 10 minutes. About 300 miles northwest of Bermuda, the captain turned the seatbelt sign back on. About 3 minutes later, the airplane encountered moderate turbulence. During that time, two passengers and a flight attendant fell as they were attempting to sit down. The passengers sustained minor injuries, and the flight attendant fractured her pelvis. The flight subsequently landed uneventfully at BOS, and was met by medical personnel.