An influential panel of U.S. experts issued final recommendations on Monday reaffirming their controversial position that mammogram screening should start at age 50, but also said some women may benefit from screening starting at age 40. Under the U.S. Preventive Services Task Force guidelines, mammogram screening every two years for women 50 to 74 got a grade of "B", meaning doctors should offer the service. Screening for women in their 40s got a "C" grade, meaning doctors should offer the service for select patients, depending on individual circumstances. Critics have stressed that keeping 50 as the starting age for screening could threaten insurance coverage for millions of women aged 40 to 49.