UnitedHealth Group, the largest insurance company in the U.S., on Thursday slashed its earnings outlook, citing new problems related to Obamacare, and told investors it may exit the program’s exchanges.

“In recent weeks, growth expectations for individual exchange participation have tempered industrywide, co-operatives have failed, and market data has signaled higher risks and more difficulties while our own claims experience has deteriorated,” Stephen J. Hemsley, chief executive officer of UnitedHealth Group, said in a press release.