Answer: You would use V13.29 (Other genital system and obstetric disorders) if the patient had a history of this and you were seeing her as a patient before she got pregnant.
Go to the V23 category codes for supervision of a high-risk pregnancy. You should look at V23.49 (Pregnancy with other poor obstetric history) for a placental abruption. This means the patient had the problem in her previous pregnancy and the placental abruption code from the ob chapter was reported. Now, though, you are monitoring her in case it happens again, which it has not. Now she is just a high-risk patient, and the code to use is V23.49.