This may happen if too many programs come in violation of the 80 hour workweek trying to get the surgical #'s needed. If surgical #'s decline then ACOG will institute an additional year but then again this will be true for many other residencies besides OB. The biggest hurdle is after on call for 24 hrs no new patients, which means a 7-8am case may not be performed by an on-call resident (usually this means the first/second years miss out on cases).