Much of what Dr. Thomas J. Benedetti had to say about operative vaginal delivery was true, but several things warrant further discussion ("Weigh Odds of Success Before Applying Vacuum Extractor," Feb. 15, 2000, p. 19).
His comments about a reasonable expectation that the device will work were straightforward. They did not convey, however, the difference between an unsuccessful trial and a failed operative vaginal delivery (OVD). These terms are not interchangeable, and for medicolegal reasons a distinction should be made.
By definition, an unsuccessful trial implies some a priori uncertainty of outcome that is clinically acceptable. Intrapartum events enable most practitioners to use common sense about patient candidacy for a trial of OVD as well as to arrange for prompt abdominal delivery if necessary.
A failed OVD implies a priori certainty of outcome and therefore misjudgment on the part of the clinician, injury to the fetus or patient, or both.
Dr. Benedetti was correct when he implied that forceps and vacuum should be viewed as equal in terms of indications, prerequisites, and inherent risks. For example, if it is too high for forceps, then it is also too high for vacuum. The American College of Obstetricians and Gynecologists' educational bulletin on OVD is clear about the relationship between station and safety.
The results of Dr. Dena Towner's study are intriguing but not really surprising to experienced accoucheurs (N. Engl. J. Med. 341:1709-14, 1999). Most of the previous literature, unfortunately, has focused on the instrument and not on the intrapartum events that necessitate OVD.
The safety of combination vacuum-forceps and forceps-vacuum deliveries has been debated before, but very little data are available to address efficacy. I cannot think of any clinical situations in which the latter combination is justifiable.
I have experienced several cases in which caput and molding have caused the vacuum to slip off, but I was able to subsequently complete the delivery with forceps.
Finally, I am unaware of any data (anecdotal or published) to support Dr. Benedetti's proposition that occiput posterior presentations should be preferentially delivered by forceps. Practitioners should use the instrument that they feel most comfortable with.
Dirk E. Peterson, M.D.
Fort Myers, Fla.
Dr. Benedetti replies:
I want to thank Dr. Peterson for his interest in my opinions on this subject. I wish to respond to two items he raised.
I know of few, if any, instances in which a physician knows with certainty the outcome of any surgical procedure. I think that Dr. Peterson's distinction between unsuccessful and failed operative delivery is a semantic one and without medical or legal application.
I made my recommendation regarding the use of forceps rather than vacuum for occiput posterior deliveries on the basis of two medical findings.
The first is the known requirement for increased traction necessary for delivery of occiput posterior as opposed to occiput anterior. If the traction force necessary for delivery exceeds the release force of the vacuum cup, repeat applications or abandonment of the vaginal procedure might occur more often when forceps might have succeeded.
The other reason to be cautious with the use of the vacuum with occiput posterior presentations is the observation that there are more "pop offs" with the centrally inserted traction handle than with an offset traction handle insertion. All of the current devices have the centrally inserted traction device and are subject to more pop offs.