Tetracycline should not be given to pregnant women. It can cause permanent discoloration of the fetus' teeth, including the adult teeth.
When Danny identified who the car was registered to, he stated the owner was Elizabeth Barker, a "Caucasian female, 25 years old," which placed her in the right age window as the victim, since Hawkes determined the victim was "between the ages of 17 and 25." Toward the end of the episode, Flack puts out an alarm on a "Caucasian female, 30 years old, name Elizabeth Barker."