Saying it is “seeing further signs of an unbalanced risk pool,” Humana announced on Tuesday that it is exiting the health insurance exchanges set up under the Affordable Care Act (ACA), which may be moot if the Republicans in Congress carry out their threat to “repeal and replace” Obamacare, though their timetable is uncertain.

Humana last year already drastically scaled back its involvement in the exchanges, as did UnitedHealth Group. In 2016, Humana announced it would limit offering individual insurance plans to “no more than 156 counties” – a reduction of 1,195 counties on and off the ACA federal marketplace – after it stopped selling ACA plans in at least four states.

Meanwhile, overall enrollment in ACA health plans dropped this year by some 500,000 persons for a total of 9.2 enrollees and rollovers, the first drop in four years of the program.