We thank Dr Kreitzer for his continuing communications on shoulder dystocia and comments on our work.

We agree that subjective definitions and imperfect record keeping are limitations with most studies on shoulder dystocia; however, we would like to point out an incorrect assumption in the letter. In our study, incidences of shoulder dystocia were not determined by retrospective chart review, which would potentially add recorder bias issues. The diagnosis was recorded prospectively in the delivery record by the delivering clinicians at the time of the birth.

Very few centers use the prolonged head-to-body interval as the sole criterion for diagnosing shoulder dystocia. Most use the standard American Congress of Obstetricians and Gynecologists definition. Use of a prolonged interval increases the “observed” rate of shoulder dystocia several-fold to the range of 13.7-16% of vaginal births. Most of the increase is in the mild variety with little clinical consequence. Clearly, different definitions result in different incidence numbers; the key is to use a clear and consistent definition and to report rates for both the complicated and uncomplicated forms of shoulder dystocia.

As discussed in the article, the perceived need or maneuver is to a degree subjective and “…changing shoulder dystocia rates are always open to interpretation as to whether the actual condition was changing or possibly only diagnostic criteria were applied differently. Therefore, we also examined a subset of the total shoulder dystocia group that had an additional objective marker of a difficult shoulder dystocia delivery, namely those with any BPI or need for immediate intubation, bag and mask ventilation or fracture.” The fact that these complicated shoulder dystocia rates were also falling during the course of the study, coupled with no change in either uncomplicated or complicated shoulder dystocia rates among the physician group without access to the program, increased our confidence that a real change was occurring rather than a simple change in institutional practice of diagnostic labeling.

Dr Kreitzer expresses an interest in studies to determine the optimal management of shoulder dystocia. We note that better methods to detect the few women who are at very elevated risk so they may be offered cesarean delivery and better techniques to deliver unexpected cases are complementary approaches. We welcome more studies to shed light on this difficult subject.