"Desperate Housewives" star Marcia Cross is facing a serious pregnancy complication she fears could jeopardize the health of her unborn twins.

A recent ultrasound revealed the 44-year-old actress, who is due in April, is suffering from placenta previa, say pals. The condition is caused by all or part of the placenta covering the opening to the cervix.

And one insider maintains that a panicked Marcia recently rushed off the "DH" set and headed straight to her doctor's office when she started suffering from cramps and bleeding.

"Marcia's doctor checked the fetuses' heartbeats, and found them to be perfectly healthy," a source close to the actress told The ENQUIRER.

"Marcia was relieved, but her doctor warned her that she had better slow down and take things easy."

The doctor also performed an ultrasound on the fetuses and discovered the placenta previa, says the source. Placenta previa is a potentially life-threatening condition that causes the placenta to precede the baby during birth, and severe hemorrhaging can occur during labor.

"The problem might resolve itself as the fetuses grow and pull the placenta away from the danger area — but if it doesn't work itself out, it could endanger both her and the twins," added the source.

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