Net income at Cigna Corp., the Philadelphia based health, life and disability insurance company, dropped 18 percent in the first quarter, even as enrollment in health insurance plans increased nine percent over the year - the highest total since 2003.

Cigna shares dropped to $150.04 from yesterday's close of $155.21, but settled in at around $154 a share mid-day.

Net income fell from $352 million in the first quarter of 2006 to $289 million, but diluted earnings per share rose from $2.87 to $2.93 because the company repurchased 4.2 million shares for $575 million during the first quarter.

Most of the income drop is attributable to an investment gain in the first quarter of 2006. The company sold some of its investments, earning $94 million in that quarter.

In the 2007 first quarter, investment income was at its more regular level of about $13 million. Income from operations increased year over year from $258 million to $264 million.

The company expects 2007 earnings per share on adjusted income from operations to be in the range of $10.25 to $10.95, better than its early forecast.

Revenue from premiums and fees rose to $3.7 billion from $3.3 billion a year ago. Overall revenues rose from $4.1 billion to $4.37 billion.

Contact staff writer Jane M. Von Bergen at 215-854-2769 or jvonbergen@phillynews.com