NEW YORK (Reuters) - U.S. life and mortgage insurer Genworth Inc (GNW.N: Quote, Profile, Research) said on Thursday that net income fell in the fourth quarter, hurt by investment losses, and it was adopting a "cautious stance" for 2008.

The Richmond, Virginia-based company posted a net profit of $178 million, or 40 cents a share, compared with $373 million, or 81 cents in the year ago period.

Net operating income, which is used by analysts to measure performance, was $314 million, or 71 cents per share, compared to $355 million, or 77 cents per share, in the fourth quarter last year.

While both net income and operating profit were lower than a year ago, the results beat average analysts expectations of 68 cents a share, according to Reuters Estimates.

The company said the quarter included a $2 million reduction in a previous gain, and net investment losses of $134 million, including $123 million of impairments, three-quarters of which were related to sub-prime and Alt-A residential mortgage and asset-backed securities.

"We have a cautious stance toward 2008 results, given the accelerating downturn in the U.S. housing market, slowing global economies and a shifting interest rate environment," said Chief Executive Michael Fraizer, in a statement.

Genworth said it now expects operating earnings per share in 2008 to be at the lower end of its previously announced range of $2.65 to $3.15. It will fully update its outlook at the end of the first quarter, it added.

(Reporting by Lilla Zuill, editing by Phil Berlowitz, Leslie Gevirtz)