The water's still not great in those Obamacare "risk pools," Aetna 's CEO says. Aetna's Chief Mark Bertolini said Tuesday that the big health insurer sees further "deterioration" in the financial risk of covering the pool of Obamacare customers — increasing pressure on insurers in the few states where Aetna continues selling individual health plans, as well as in other states the company exited this year.