Mortgage insurer MGIC Investment Corp. (MTG) narrowed its fourth-quarter by 37% from last year, but the firm’s bottom line is still suffering from mortgage defaults that occurred in recent periods.

The company said it successfully secured a deal with Fannie Mae, Freddie Mac and the Officer of the Commissioner of Insurance for the State of Wisconsin to continue writing new business outside the capital guidelines currently required in the state and by the government-sponsored enterprises.

The Milwaukee-based insurer posted a loss of $135.3 million, or 67 cents a share, for the three months ended Dec. 31. That compares to a loss of $186.7 million, or 93 cents a share, a year earlier.

The loss for the full year hit $485.9 million, wider than the $363.7 million loss recorded in 2010.

Fourth-quarter revenue rose to $447 million, up from $361.1 million a year earlier. Net premiums in the quarter declined a bit falling from $271.4 million in the fourth quarter of 2010 to $268.3 million in the most recent quarter.

The percentage of delinquent mortgages, excluding bulk loans, insured by the firm fell from 14.94% in December 2010 to 13.79% in 2011. When including bulk loans, the delinquency rate is now 16.11% of the entire insured portfolio.

MGIC, like other mortgage insurers, has the goal of raising capital in a tough mortgage lending market. With the Wisconsin regulator and the GSE’s waiving certain new issuance requirements, the firm has the opportunity to avoid a regulatory snag while pursuing more business.

During the fourth quarter, the company wrote $4.2 billion in new insurance, which is flat with the previous year. The Home Affordable Refinance Program accounted for approximately $812 million of insurance.

Write to Kerri Panchuk.