Rule of thumb is that the OB global period begins on the visit when the antepartum record is started. If the patient comes in for confirmation that she is pregnant (eg urine pregnancy test), and the antepartum record is not started, most payers will allow a low-level E/M with the V code for pregnancy confirmed. The antepartum record (and global period) starts with the next visit. Likewise, if pt comes in for a well-woman exam knowing she is pregnant, it is okay to bill the well woman exam and have her return for the first antepartum visit. Hope this helps.
Patricia A Hubbard, CPC