When open enrollment in Obamacare starts next month, enrollees in four states will be able to choose plans from only one insurer.

Alaska, Alabama, Wyoming and Oklahoma have confirmed to the Washington Examiner that they will have only one insurer offering Obamacare plans for 2017. The revelation comes in the wake of defections from some major insurers that have left Obamacare exchanges due to financial losses.

A lack of competition could mean no driving force to offer lower prices to consumers. Some states have approved rate increases of up to 50 percent. A recent independent estimate on the site acasignups.net predicted that 25 states have approved average price hikes of nearly 25 percent.

Of the four states, only Wyoming had one Obamacare insurer during the last open enrollment, according to an August study from the nonpartisan Kaiser Family Foundation.

Alabama was hit particularly hard by insurer defections. Last year, the company had three insurers offering plans: Blue Cross Blue Shield, UnitedHealth and Humana. Now only Blue Cross Blue Shield will offer Obamacare plans as UnitedHealth and Humana are leaving the state, said Mark Fowler, chief of staff for Alabama's Department of Insurance.

UnitedHealth announced earlier this year that it is exiting a majority of the 34 states it offers Obamacare plans in due to losses. The company has said it expects to lose about $400 million this year, primarily due to higher medical claims than anticipated.

Humana is exiting four of the 15 states it offers plans in, also citing financial problems.

In addition to Humana and UnitedHealth, Aetna announced it would withdraw from about 70 percent of its total Obamacare markets. While the company has said the decision was based on losses, some Democrats have speculated that the company did it in retaliation for the Department of Justice suing to block a merger between Aetna and Humana.

The Justice Department also blocked a merger between Anthem and Cigna, which have both remained committed to the law.

The Department of Health and Human Services did not return a request for comment on the state of Obamacare competition.

The number of states with only one insurer is, however, below prior studies that estimated more states would have a single carrier. For example, consulting firm Avalere health in July estimated that seven states would have only one carrier.

Some estimates also pointed out that some states have more than one insurer, but only for a small part of the state. For instance, Kaiser predicted that Mississippi would have only one insurer for 80 percent of the state and two insurers for 20 percent. Florida will have one insurer for 73 percent of the state, two for 12 percent and three insurers or more for 10 percent.

However, the estimates were released in August, before the Sept. 23 deadline for plans to enter the marketplace. The Examiner contacted the four states with only one insurer after the Sept. 23 deadline and they said they did not have new market entrants.

The other states besides the four with one insurer initially predicted by Avalere were Kansas, North Carolina and South Carolina.

Kansas' insurance department told the Washington Examiner that it will have three carriers for 2017, and North Carolina will have two carriers. Meanwhile, South Carolina said it would have its data by Oct. 7.

While North Carolina will have two carriers, only Blue Cross Blue Shield will cover the entire state. Cigna will enter the Raleigh area to offer plans.

The entrance is part of a greater expansion for Cigna. Other new markets include Chicago, St. Louis, Kansas City, Northern Virginia and Richmond. Cigna also is expanding in existing markets in Colorado, Arizona, Tennessee and Maryland.

However, Cigna did not offer a lifeline to the four states that are facing just one insurer.

Some insurance regulators said that only having one carrier wouldn't disrupt coverage for residents.

"Even though we have just the one carrier, our market appears to be fairly stable as Blue Cross Blue Shield of Wyoming is a healthy company and we have not received any indication they [are] considering existing the market," said Denise Burke, senior policy and planning analyst for Wyoming's Department of Insurance.