Government-sponsored enterprise (GSE) Fannie Mae ($0.00 0%) purchased $46bn of loans out of mortgage-backed security (MBS) trusts in April 2010 as part of an effort to buy-out seriously delinquent pipelines.

The loan purchases will not appear as liquidated from MBS until May 2010, according to a monthly summary of the GSE's books (download here).

Excluding these repurchases, and the liquidation impact of the previous month's repurchases, Fannie's total book of business would have contracted at a 4.2% compound annualized rate.

Taking into consideration the substantial buy-outs, the total book of business contracted at a compound annual rate of 1.9% to nearly $3.26trn in April.

Fannie's gross mortgage portfolio grew at a compound annual rate of 46.4% to $789.49bn in April.

The seriously delinquent rate of Fannie's single-family mortgages fell 12 basis points (bps) to 5.47% in March, the most recent month of data. At the same time, the seriously delinquent rate of multifamily mortgages grew 6 bps to 0.79%.

The April figures arrive after the close of Q110, in which lenders repurchased approximately $1.8bn in loans from Fannie, measured by unpaid principal balance, after the loans failed to meet the GSE's standards.

Write to Diana Golobay.

Disclosure: the author holds no relevant investments.