Aetna Inc, the third largest U.S. 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. An estimated 30 million more people are expected to join the insured over the next decade because of the U.S. Patient Protection and Affordable Care Act of 2010. Millions of those will seek their health insurance through the exchanges.