UnitedHealth Group Inc posted a higher-than-expected fourth-quarter profit, helped by moderating use of medical services by its members and enrollment growth across its health insurance plans.

UnitedHealth also announced a shuffling of its top management, including a new chief financial officer, that could set up succession plans at the largest U.S. health insurer by market value.

UnitedHealth, the first insurer to report fourth-quarter results, backed its 2011 profit forecast while raising its revenue projection slightly.

Health insurers benefited throughout 2010 from more people postponing doctor visits and procedures to save money, and UnitedHealth had previously suggested its fourth-quarter results could beat expectations if the use of medical services remained low.

I expect utilization to remain moderate, and if it does, there's probably upside to current guidance, Wedbush Securities analyst Sarah James said.

UnitedHealth shares fell 0.6 percent to $40.30 in premarket trading. The stock had risen 12 percent in 2011, compared with an 8.5 percent increase for the Morgan Stanley Healthcare index <.HMO> of health insurers and a 2 percent rise for the broader Standard & Poor's 500 index <.SPX>.

Sanford Bernstein analyst Ana Gupte said called it a very strong quarter but said investors might look for some weakness in the stock before buying shares, noting the stock's recent run.

Insurers face new rules this year from the healthcare overhaul passed in 2010 that will require them to meet spending thresholds for medical care as opposed to administrative costs and profit.

UnitedHealth, whose diversity and size make it a bellwether for the industry, said fourth-quarter net income rose 10 percent to $1.04 billion, or 94 cents per share, from $944 million, or 81 cents per share, a year earlier.

Analysts on average had expected 84 cents per share, according to Thomson Reuters I/B/E/S. Some analysts also excluded a charge for a sale from their calculations, making the beat even greater than 10 cents per share.

Revenue rose 10 percent to $24.03 billion. Analysts had expected $23.75 billion.

ENROLLMENT UP ACROSS THE BOARD

Enrollment in UnitedHealth's plans rose 3 percent to 37.5 million.

Enrollment in its commercial plans serving employers increased 8 percent. Membership in its Medicare Advantage plans for the elderly rose 16 percent, while its Medicaid plans for low-income Americans grew 14 percent.

The various business lines seemed to perform well, with enrollment up sequentially in every reportable segment, Wells Fargo analyst Peter Costa said.

The company named David Wichmann, who had previously been president of the company's operations, as chief financial officer. He replaces Mike Mikan, who will take responsibility for oversight of health services, such as its information technology businesses, an area where the company is placing greater emphasis.

UnitedHealth also said Gail Boudreaux would assume responsibility for all of UnitedHealth's health benefits businesses, widening her scope beyond commercial plans.

The appointments, effective immediately, appeared to be setting up a possible horse race among the three executives to succeed Chief Executive Officer Stephen Hemsley. Hemsley, 58, had his contract renewed in December for four years.

The company also said it intended to sell its clinical trial support businesses for mid- and late-stage studies to privately held inVentiv Health. UnitedHealth did not specify the sale price, but Citigroup estimated the unit to be worth $400 million to $500 million.

UnitedHealth continues to forecast 2011 earnings per share at $3.50 to $3.70, representing a roughly 12 percent decline from 2010.

The Minneapolis-based company said it expected 2011 revenue at the top end of its prior forecast range of $99 billion to $100 billion, citing strong customer retention, growth across its businesses and contributions from recent deals.

(Reporting by Lewis Krauskopf; Editing by Lisa Von Ahn and Gerald E. McCormick)