UnitedHealth said in October that it would spend about $4.9 billion to buy a majority stake in Brazilian health benefits and care provider Amil Participacoes SA. The company is the largest health insurer in Brazil and also owns hospitals and clinics.
The insurer's enrollment jumped 18 percent in the quarter to 40.9 million people, compared to the 2011 quarter. That was largely due to the addition of the Brazilian business.
For the full year, UnitedHealth earned $5.53 billion, or $5.28 per share, on $110.62 billion in revenue.
The company said it still expects 2013 earnings to range between $5.25 and $5.50 per share on $123 billion to $124 billion in revenue.
Analysts expect, on average, earnings of $5.56 per share on about $122.1 billion in revenue.
UnitedHealth is the first insurer to report earnings every quarter, and many see it as a bellwether for the sector. WellPoint Inc. will be the next major insurer to report on its fourth quarter when it releases results Jan. 23.
UnitedHealth shares rose 74 cents to close at $54.40 Thursday, while the Dow Jones industrial average — of which UnitedHealth is a component — also climbed less than 1 percent.
Last year, UnitedHealth shares were up 7 percent to close 2012 at $54.24.