NBC's fall drama "Parenthood" has been pushed from a fall launch to a midseason premiere due to the illness of series co-star Maura Tierney.

"Parenthood," based on the 1989 Ron Howard film (already developed once previously for the small screen), was expected to begin production on July 27 and NBC had set a September 23 premiere date for the 8 p.m. drama.

"Start of production on NBC Universal's new series 'Parenthood' has been postponed for eight weeks due to medical evaluation that valued cast member Maura Tierney is undergoing," NBC said in a statement to The Hollywood Reporter. "The top priority for NBC, Universal Media Studios and Imagine Television is the well-being of Ms. Tierney. We are unable to release further details and ask that you respect her privacy at this time." 

"Parenthood" is now tentatively scheduled to resume production in September, though obviously that's subject to change.

In addition to long-time NBC veteran Tierney ("NewsRadio," "E.R."), "Parenthood" stars Peter Krause, Tierney, Erika Christensen, Dax Shepard, Bonnie Bedelia and Craig T. Nelson.

The medical dramedy "Mercy," expected to take over the "Parenthood" time slot at midseason, is expected to be bumped up for a fall launch, though it's unclear if NBC will simply move it into the Wednesday 8 p.m. hour or make additional changes.

"Mercy" is the latest in a new wave of nurse-centric medical shows. Its stars include Taylor Schilling, Michelle Trachtenberg, Jaime Lee Kirchner, James Tupper, James LeGros and Delroy Lindo.