Health insurance giant Aetna said Wednesday that it will not be participating in any Obamacare exchanges in 2018.

"Our individual commercial products lost nearly $700 million between 2014 and 2016, and are projected to lose more than $200 million in 2017 despite a significant reduction in membership," T.J. Crawford, Aetna spokesman, said in an email.

The reason for the losses, he said, came from structural issues within the exchanges "that have led to co-op failures and carrier exits, and subsequent risk pool deterioration." He did not cite uncertainty over the future of Obamacare, as the company had done when it announced last week that it would be exiting the exchange in Virginia.

Aetna also announced in early April that it would be pulling out of the exchange in Iowa, and the latest announcement adds Delaware and Nebraska to that list, both on and off the exchange.

Insurers have lost money in the exchanges for a variety of reasons, including that not enough young and healthy people enrolled in the federally-subsidized plans to offset the cost of covering older and sicker individuals with higher medical spending.

Aetna had participated in several Obamacare exchanges, but dramatically reduced its participation for 2017 soon after the Obama administration's Department of Justice challenged the company's planned merger with Humana. The federal judge who decided the antitrust case, effectively blocking and terminating the merger, wrote in his opinion that Aetna appeared to reduce its exchange participation as backlash against the Obama administration's attempt to block the merger. Aetna has maintained its decision to leave the exchanges was based on $450 million in losses it suffered in 2015 on account its exchange participation.