(Reuters) - Insurer Cigna Corp (>> CIGNA Corporation) posted a lower-than-expected first-quarter profit on Thursday, as earnings slipped in its segment offering disability and life coverage policies.

Cigna is the latest health insurer to miss Wall Street's earnings target in the period, following Aetna Inc (>> Aetna Inc.), Coventry Health Care (>> Coventry Health Care, Inc.) and Humana Inc (>> Humana Inc.).

Cigna did raise its full-year earnings forecast.

Net income fell to $371 million, or $1.28 per share, from $413 million, or $1.51 per share, a year earlier.

Excluding special items, Cigna's earnings of $1.28 per share fell 2 cents below the analysts' average estimate, according to Thomson Reuters I/B/E/S.

Revenue jumped 25 percent to $6.79 billion, helped by the acquisition of Medicare specialist HealthSpring.

Profit in the main healthcare segment rose 6.5 percent to $262 million, helped by rising membership in its plans.

But earnings in its disability and life segment fell 16 percent to $65 million. The company cited strategic investments in its disability management programs as a factor pushing down profit.

Cigna forecast 2012 earnings of $5.20 to $5.55 per share. It previously projected $5.00 to $5.40. Analysts have been looking for $5.41.

(Reporting by Lewis Krauskopf in New York; Editing by Lisa Von Ahn)