NEW YORK, Dec 13: Aetna Inc, the third largest US health insurer, said on Wednesday that by 2014 it expects to be part of about 15 healthcare exchanges being established under government reforms. Aetna, one of the companies on the front lines of healthcare changes in the United States, told analysts and investors that it believes an increase in the number of customers from the new market places will likely contribute to its growth. (agencies)