The insurer warned earlier in the day that losses from its Obamacare individual insurance plans will likely continue, despite pulling out of the exchanges in 11 of the 15 states it sells the plans.
"We need to fix the risk adjustment program. This population has clearly got more morbidity than had been initially anticipated. If we can fix risk adjustment, we can stabilize the market, but until that happens, it's only going to get worse," Bertolini said in an interview with "Closing Bell."
The risk adjustment program is meant to prohibit risk selection by insurers by transferring funds from plans with lower-risk enrollees to ones with higher-risk people.
However, Bertolini said the mechanism is not paying out.
"All it's doing is transferring risk from companies that are losing less money to companies that are losing more money so we all lose the same money. Until we fix that game, until we fix that part of the process, it will not change," he said.
The earliest Aetna may return is 2019, more likely 2020, and only if operations improve.
"Before we go back on, we need legislative change. That's what it's going to take to get the risk adjustment mechanism fixed," Bertolini said.
Therefore, a return to the market by 2018 would be a "miracle," since the new Congressional session doesn't begin until early January and pricing for 2018 is due by April 1, 2017, he explained.
"I just want a Congress than can work with a president."
If it is Clinton as president and a Democratic Congress, he anticipates fixes to Obamacare. If it is a Republican sweep, he sees a move toward extending Medicare down to chronically ill people who are over 55, as well as an expansion of Medicaid.
"These two programs, with in-place risk adjustment mechanisms, with solid systems to track eligibility and enrollment, would have worked much cheaper than implementing the Affordable Care Act," he said.
— Reuters contributed to this story.