NBC puts "Parenthood" on hold

NBC confirmed Saturday the announcement of the postponement of production on a new show, "Parenthood."

Star of the new nighttime drama Maura Tierney is said to be undergoing a "medical evaluation," says MSNBC.com.

"Parenthood," which was set to premiere Sept. 23, has been postponed until midseason "due to a medical evaluation that valued cast member Maura Tierney is undergoing," said a statement on Entertainment Weekly's Web site.

"The top priority for NBC, Universal Media Studios and Imagine Television is the well-being of Ms. Tierney," the statement added. "We are unable to release further details, and ask that you respect her privacy at this time."

Tierney, 44, plays Sarah, one of four adult children. The drama portrays the relationship between four siblings and their parents. "Parenthood," is Tierney's follow up to her decade long role as nurse Abby Lockhart, on the well-known medical drama, "ER."

NBC will now debut "Mercy," a new medical drama, this fall, in place of the postponed show.