Health insurer Aetna said on Thursday that its second-quarter operating earnings would exceed the current analysts' average forecast of 68 cents per share.

The company, which will be disclosing the forecast in a presentation to investors at a Goldman Sachs healthcare conference, said the result was being driven by a better-than-expected underwriting margin, largely attributable to favorable development of first-quarter healthcare cost estimates.

Aetna said it would update its full-year 2010 outlook on its second-quarter conference call.

In April the company told investors that 2010 was a "repositioning year," due to re-pricing its commercial plans to reflect increased medical costs that pulled down results in 2009.

Aetna projected full-year operating earnings of $2.75 to $2.85 a share in 2010.

Shares of Aetna were up more than 2 percent at around $29.99 in early New York trading.