Obstetric nurses Abby seems to be a hybrid of physician and staff nurse. She would NOT be sent there to act as physician because no docs were available. Breaks are canceled in an emergency. Apparently Abby also abandoned her labor patient without signing her out to another nurse since we later have Coburn chastising her for not being there for the birth. This would be ground for dismissal, one would think she would have notified her nurse manager, particularly when she was delayed.
Anomalies are a different matter altogether.
This require extensive training, frequent practice and takes at least 20-30 minutes to do a passable job. Apparently Abby attended school and trained as an ultrasound technician between nursing and medical school. Of course, she also diagnosed a tubo-ovarian abscess with an ultrasound in Such Sweet Sorrow, so I guess she is crosstrained in multiple areas. She later is seen making decisions such as refusing to transfer her patient despite the trauma room being needed for other cases. This is outside the scope of her duties as a nurse and would endanger her job.