While the American Horror Story's first season finale was originally planned at 2 hours, we have news that the finale has been shortened. Deadline is reporting that the fast paced shooting schedule for the first season has resulted in the finale being trimmed down to 90 minutes:

"The project was picked up to pilot in late February. Creators Ryan Murphy and Brad Falchuk couldn’t work on the pilot until they wrapped the second season of Glee, so it didn’t start shooting until late May. In a quick turnaround, FX picked up the pilot to series on July 18, and it was rushed to production 2 weeks later to make the Oct. 5 premiere date. With the first episode after the pilot doing some reshoots and some of the episodes requiring 8-day shoots vs. the standard 7 because of complex scenes, production on the series is now at a point where Episode 13 would wrap on Dec. 15, leaving no time for post-production to make the Dec. 21 air date."

American Horror Story has already been renewed for a second season, but we have good news or fans of the show. FX is considering a higher season order than the originally planned 13-episode second season. We'll be sure to post an update as soon as anything is made official.

Source: Deadline