Health insurance startups like Bright and Oscar have raked in $3 billion in venture funding. They're using that war chest to plot out massive expansions across the US.

For the first quarter of 2019, Clover's financial losses narrowed.

Clover lost $9.3 million, according to state insurance filings reviewed by Business Insider, down from the $14.7 million the company lost in the first quarter of 2018. The company sells private health-insurance plans for seniors, a market known as Medicare Advantage.

Clover generated $115 million in revenue across its health plans in seven states. The company paid out $109 million in medical expenses for its customers over the quarter, or about 95% of the premium revenue it took in, similar to its results from 2018.

The company recruited more members in 2019. Clover had 40,137 Medicare Advantage members at the end of the first quarter, up from 32,425 at the end of 2018.

It's already been a big year for Clover. In March, the company said it was laying off 25% of its workforce, or about 140 employees, as part of a restructuring. That came on the heels of Clover raising $500 million in January, bring the total funds the company has raised to $925 million.

Clover got its start selling Medicare Advantage plans in New Jersey, which remains the company's main market. The company also operates in Pennsylvania, Texas, Tennessee, Georgia, South Carolina, and Arizona. It's still unclear whether Clover will enter new markets in 2020 and a spokesman for the company declined to comment.

Read more: We took a look at the latest financial results for health insurer Clover Health, which raised $500 million in January and laid off 25% of its staff in March

Oscar Health has been offering health plans since 2014, amassing a national presence and hundreds of thousands of members. The company mainly sells health insurance to individuals in the markets created by the Affordable Care Act.

For 2019, Oscar offered health-insurance plans in nine states: Arizona, California, Florida, Michigan, New Jersey, New York, Ohio, Texas, and Tennessee.

Documents reveal the company plans to operate in Philadelphia and nearby Delaware county in Pennsylvania next year. Oscar has also filed to be an insurer in Illinois and Georgia.

Oscar has said that it's planning to offer a new type of health insurance as well. In 2020, Oscar will start offering Medicare Advantage plans. The company hasn't yet said where it will sell those plans.

Oscar in May provided reporters with a summary of its financial results for the first quarter of 2019. The company said it took in $354 million in gross premium revenue, and that it generated a gross underwriting profit of $82 million. The company said it spent about 70% of its members premium dollars on medical care.

The figures that Oscar provides are adjusted to account for a reinsurance agreement with insurance giant Axa.

According to the filings reviewed by Business Insider, Oscar posted a net profit of $24 million in the first quarter of 2019.

Read more: We got our hands on filings that show $3.2 billion health-insurance startup Oscar Health is plotting an expansion into another city

Devoted Health is already plotting a geographic expansion beyond Florida, its first state.

State insurance filings reviewed by Business Insider show that Devoted has registered as an insurer in Texas, suggesting the company might start offering plans there. Devoted has previously declined to comment on its plans.

Devoted was founded to sell Medicare Advantage plans, or private health insurance to US seniors, a market that's growing rapidly. The company was valued at $1.8 billion, before it began covering a single customer.

For the first three months of 2019, the company posted a net loss of $1.5 million for its plans in Florida, according to the filings.

Devoted covered about 2,489 people at the end of March. In the first quarter, the company took in $8 million in premium revenue and spent more than that, an estimated $8.2 million, on medical care in the first quarter. Health insurers generate profits by spending less on medical care than they receive in premiums.

Read more: We just got our first look at $1.8 billion startup Devoted Health's financials since the health insurer began signing up customers

Aside from massive funding rounds, among all four startups, there's one unifying factor: They all offer or plan to offer Medicare Advantage plans.

Both Oscar and Bright also have a presence on the individual exchanges set up by the Affordable Care Act. For 2019, 11.4 million people signed up for a plan on the exchanges nationally.

The market for Medicare Advantage plans his competitive. About a third of people on Medicare are enrolled in private Medicare Advantage health plans. People can typically choose to enroll in Traditional Medicare or Medicare Advantage plans when they turn 65. Either way, their health needs are largely funded by the US government.

As of last year, more than 20 million Americans were enrolled in Medicare Advantage plans. It's a growing market that insurers from startups — including these four — are interested in getting a piece of, alongside entrenched rivals like Humana, UnitedHealth Group, and CVS Health are in.

It remains to be seen how sizeable of a presence these newer entrants can amass through expansions within existing states and how key geographic expansions will be to their strategies as well.