Aetna Inc., the No. 3 U.S. health insurer by membership, raised its earnings forecast for the year after first-quarter profit topped analysts’ estimates, helped by rising premiums.

The health insurer now expects 2016 earnings of $7.90 to $8.10 a share, excluding some items, up from a February forecast of at least $7.75, according to a statement Thursday. Analysts anticipated $7.95, the average of predictions compiled by Bloomberg.

Aetna has added customers in the private Medicare Advantage program for the elderly, and is expanding its wager on the business with the planned acquisition of Humana Inc. That helped cushion a decline in commercial membership and a rise in medical costs.

• First-quarter net income fell 6.5 percent to $726.6 million, or $2.06 a share, from $777.5 million, or $2.20, a year earlier

• Operating earnings per share of $2.30 tops the $2.23 average of analysts’ estimates

• Medical loss ratio widened to 80.5 cents per premium dollar, compared with spending 79.1 cents per dollar a year earlier

Aetna has one of the largest numbers of members in the new marketplaces created by the Affordable Care Act, according to Bloomberg Intelligence. Large health insurers have been struggling to make a profit from these so-called Obamacare exchanges, and in February, Aetna Chief Executive Officer Mark Bertolini said he had “serious concerns about the sustainability” of those markets.