The CPT® book defines which services may be billed outside of the global OB package, and what services are included in the package. The start of the maternity care codes in the CPT® book describes the antepartum care services, including frequency and exam.
The American College of Obstetrics and Gynecology (ACOG) has written an article which can be found in the citations section, which is helpful. It describes common scenarios, such as patients who transfer in or out of the practice during their pregnancy.
The CPT® book has long included direction about how to bill for complications or other problems provided by the OB doctor during pregnancy. If the patient has a complication of pregnancy, or an acute problem, and is seen more frequently than at the intervals described in this section of the CPT® book, submit those separately, at the time they are performed. Use the medical diagnosis first and the pregnancy diagnosis separate. It requires a separate progress note, not simply the entry on the OB form. Also, the visit should be out of sequence, that is, not one of the regularly scheduled visits.
Note that delivery services include the history and physical at the time of the patient's admission, and that is not separately reported.