In the beginning, the clock shows victim goes to bed at "11:06 Tue," then the attacker comes out of hiding at "1:06 Tue." They must have set the clock to 11AM.
The scars on Hotch's face appeared and disappeared from one scene to the other during the episode.
While looking through pregnancy records, JJ corrects Garcia by informing her that, contrary to popular belief, a pregnancy is actually ten months. In fact, nine months is correct.
Expected duration of pregnancy is placed at 40 weeks. A common mistake is to estimate each month as 4 weeks, leading to the erroneous conclusion that a pregnancy is 10 months. However, most months are a few days longer than four weeks. 40 weeks calculates as just a few days over 9 months.
The newspaper shown at the beginning of the episode is dated Tuesday, October 30, 1998. That day was actually a Friday.
When J.J. and Garcia were on the phone, Garcia's computer screen showed that she typed "Revised date parameters: August 1, 2007 - September 30, 2007" before JJ told her the date that the unsub's letter (which mentioned the insemination) was written and before Garcia said to "fast forward nine months."