Aetna Inc. has withdrawn from Connecticut's online health insurance exchange, LifeHealthPro reported. In a letter to the state's insurance department, the Hartford-based insurer said it "reluctantly" decided to withdraw from the insurance marketplace. Correspondence posted on the department's website shows Aetna and the agency disagreed over how Aetna had calculated its proposed rates. In Iowa, Coventry Health Care Inc., which was acquired by Aetna in August 2012, is one of six insurers that will offer plans on the Iowa Insurance Marketplace. Wellmark Blue Cross and Blue Shield, Iowa's largest insurer, will not participate in the Iowa marketplace until 2015.