Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Sequenom (Nasdaq: SQNM) sank as low as 10% on Friday after health insurer Coventry Health Care (NYSE: CVH) changed its mind about providing coverage for the company's prenatal Down syndrome test.

So what: Coventry was going to provide coverage to its 2.2 million members for Sequenom's MaterniT21 PLUS testing service, so the termination is naturally forcing investors to lower their revenue expectations. Of course, given that Coventry is one of the smaller companies in the health-insurance space, the loss shouldn't be too devastating to Sequenom's top line.

Now what: Aggressive bargain hunters might want to take a closer look. As William Blair analyst Brian Weinstein pointed out in a note to investors, Sequenom still expects to gain coverage for MaterniT21 PLUS from two of the six largest health insurers by the end of the year, making today's pullback a potentially profitable entry point for enterprising investors. Of course, given the company's consistent money-losing history, risk-averse conservative-types might want to maintain their distance.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.