Sequenom slumped nearly 5 percent before the opening bell Friday after the genetic test maker reported a fourth-quarter loss that was larger than most had expected.

The San Diego company said Thursday that it lost $32.8 million, or 29 cents per share, in the three months that ended Dec. 31. That was worse than the 24 cent per-share loss that analysts forecast.

Revenue did top Wall Street expectations, thanks in part to the company's Center for Molecular Medicine, which launched its MaterniT21 PLUS pre-natal test about a year ago.

MaterniT21 Plus is a blood test intended for women who are at high risk for a Down syndrome pregnancy. Sequenom says the test can detect the chromosomal anomaly that causes Down syndrome as early as 10 weeks into a pregnancy. The test also looks for two other chromosomal disorders.

But operating expenses climbed 48 percent to $41.8 million, which at into profits.

Credit Suisse analyst Dr. Vamil Divan said ihe wanted more updates than the company delivered on test volumes, covered lives and negotiations for coverage with large national health insurers. He said the lack of updates "makes it difficult to gain added comfort" from the company's story.

Shares of Sequenom Inc. fell 21 cents to $4.28 in premarket trading.