This is from ACOG:
Several factors determine how a missed delivery can be reported. These factors are, if the physician was in route to perform the delivery, if someone else in the practice performed it, and if it were performed by another physician or qualified nonphysician not associated with your practice.
Generally, when the physician has performed all the components of the global package but misses the delivery, the global package may be reported—that is, if the patient arrived at the hospital while the physician was in route and the nurse ended up performing the delivery but the physician arrived in time to deliver the placenta.
On the other hand, if the physician misses the delivery of the baby and the placenta, but arrives in time to take over from there, then it may be appropriate to bill the global code with a modifier 52 attached (i.e., 59400 -52 for a vaginal delivery). The 52 modifier indicates reduced services, since the physician did not perform the delivery. As such, the physician should consider lowering the fee to reflect the reduction in service. This reporting option should not be selected if anyone else is reporting for the delivery.
When the antepartum care, delivery and postpartum care are provided by one physician or one group, the global ob package code is reported. For instance, if the delivery was performed by another physician or nonphysician in the same practice, then the global package is reported.
Only one physician or qualified nonphysician may report for the delivery services. If a nurse midwife (not associated with obstetrician’s practice) is billing for the delivery, the obstetrician may not report the global. Therefore, each component of the ob package is reported separately. That is, report the antepartum care (59425 or 59426), delivery of the placenta (59414), episiotomy repair if appropriate (59300), and the postpartum care (59430).
When obstetricians from different groups routinely cover for each other, payers generally accept that the primary obstetrician will bill the global package and the covering physician will not bill separately. However, practices should check both their state laws and specific payer rules. In some cases, physicians may be required to report their non-global services separately.
Ultimately, coding will depend on what the physician actually performed. The physician needs to be clear in the documentation and with the insurer as to what occurred. Before reporting, it is recommended that you talk to your insurers to see what their reporting policy is, if they have one. Be sure to get the information in writing.