WellPoint ( WLP) said third-quarter net income fell to $820.7 million, or $1.60 a share, from $868 million, or $1.45 a share, a year earlier, on major investment losses.

Operating revenue in the quarter rose 2% to $15.3 billion, WellPoint said Wednesday. The company had more shares outstanding in the year-earlier quarter.

The latest quarter included net realized pretax investment losses of $562.6 million, or 71 cents a share, and an impairment charge of 17 cents a share. The quarter also included an income tax benefit of 90 cents a share.

Wellpoint, the largest U.S. health insurer, said medical membership grew by 63,000 members during the quarter and exceeded 35.3 million at Sept. 30. Its benefit expense ratio declined by 80 basis points from the second quarter.

The company said its commercial segment is performing well, as it continues to grow commercial membership while maintaining strong operating margins.

WellPoint said it narrowed its 2008 earnings forecast to $5.43 to $5.49 a share on revenue of $61.7 billion.