Unless operative vaginal delivery can be made at least as safe as cesarean delivery, it will be difficult to justify its continued existence. Proper technique is paramount.
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Operative vaginal delivery-which includes vaginal birth with the assistance of either forceps or vacuum devices-is one of the few remaining areas in obstetrics that may still be called an "art." But how long can it survive in an era of concerns about integrity of maternal tissues and short- and long-term maternal and fetal outcomes-a climate in which legal liability has contributed to ever-diminishing vaginal birth rates? Such concerns are amplified for operative (vs. nonoperative) vaginal delivery and threaten to eliminate the procedure from the armamentarium of newly trained obstetricians.
Compare trainees' experience with operative vaginal delivery to cesarean delivery. The Accreditation Council for Graduate Medical Education (ACGME) reports that in academic year 2005/2006, the national median for cesarean delivery cases per senior resident graduate over 4 years (either as primary operator or assistant) was 243 (ACGME Summary Report: Obstetrics; Residency Review Committee for Obstetrics and Gynecology, 2006). In contrast, the median 4-year experience for forceps was 11 cases and for vacuum extraction, 21. Most practitioners would agree that these numbers represent an inadequate level of training in operative vaginal delivery.
This state of affairs is likely to lead to two inexorable trends: 1 Within a generation, we will no longer have a critical mass of practitioners and teachers of the craft of operative vaginal delivery.
2 This procedure's reputation as 'dangerous' will become a self-fulfilling prophecy, as those using it will be less skilled in its application.
Together, these trends may sound the death knell for operative vaginal delivery.
The reader will decide whether the disappearance of this procedure is a good or bad trend in modern obstetric practice. But for those of us interested in preserving this delivery option, it is imperative to ensure that operative vaginal delivery is at least as safe as cesarean delivery for both mother and fetus. If this criterion of safety cannot be met, it's difficult to justify its continued existence.
Our focus here is on ways of limiting the risk of injury to the woman's perineum during operative vaginal delivery, in particular third-degree lacertions (extending to and through the external anal sphincter) and fourth-degree lacerations, which involve the rectal mucosa (Table 1). Because of the potential correlation between maternal and fetal in juries, these recommendations may have implications for the newborn, as well.
Why is it so important to avoid significant perineal lacerations? Several issues come to mind:
A Cochrane database analysis of 10 trials comparing vacuum and forceps found that vacuum was associated with a greater likelihood of failure to effect delivery (12% vs. 7%, OR 1.7, CI 1.3–2.2), greater likelihood of cephalohematoma (OR 2.4, CI 1.7–3.4), higher incidence of retinal hemorrhage (OR 2.0, CI 1.4–3.0), but less maternal trauma (OR 0.4, CI 0.33–0.5).1 In a prospective randomized clinical trial of 637 patients comparing forceps with the M-cup vacuum (a flat, rigid cup designed to be more effective than other vacuum devices for delivery of fetuses with malpresentations), there were no differences in success rates (94% efficacy with vacuum and 92% with forceps, P=0.2).2
However, the M-cup vacuum was associated with fewer third-degree (10% vs. 21%, P<0.001) and fourth-degree lacerations (2.2% vs. 7.3%, P<0.002). The vacuum was also associated with lower episiotomy rates, a variable uncontrolled in the study (30% vs. 66%, P<0.001), no difference in neonatal hyperbilirubinemia or need for phototherapy, and more cephalohematomas. The latter, however, were not confirmed by imaging (11% vs. 6%, P=0.015). Instead, diagnosis was made by clinical suspicion, which is, of course, extremely inaccurate. A 5-year follow-up study of a different randomized trial showed significantly fewer anal sphincter defects with the vacuum than with forceps (48% vs. 82%, P=0.03).3
Thus, the evidence points to lower rates of maternal perineal injury with the vacuum extractor, but higher rates of newborn head injuries, the vast majority of which are not serious (Table 2).4 Furthermore, a significant proportion of fetal injuries and failures to deliver attributed to the device may in fact be due to improper use. The commonly held belief that the vacuum extractor does not require a firm knowledge of fetal position is simply not true. Proper use of the vacuum extractor, particularly for more challenging deliveries, requires skill, judgment, training, and experience.
Therefore, I generally recommend that the trained and experienced practitioner consider the vacuum over forceps for outlet deliveries and anticipated "easy pulls."
It has long been recognized that deflexion of the fetal head, as occurs by necessity with occiput posterior (OP) presentations, is associated with dystocia and perineal injury. This is due to the substantial increase in the diameter presenting to the pelvis and perineum by the fetal head in deflexed positions (11 cm vs. 9.5 cm) (Figure 1).
The propensity of OP presentations to cause perineal injury in spontaneous vaginal birth is even more pronounced in operative vaginal delivery, as many studies have shown. In a retrospective cohort of 393 singleton vacuum deliveries, 12.2% presented as OP and 87.8% as occiput anterior (OA).6 Anal sphincter injury occurred in 42% of OP deliveries and in 22% of OA deliveries (P=0.003).
In a similar study of 588 forceps births, 12% were OP and 88% were OA presentations.7 Anal sphincter injury occurred in 52% of OP and in 33% of OA presentations (P=0.003). Of note, 16% of the deliveries categorized as OA presentations were rotated from the OP; not surprisingly, 6% of the OP presentations were inadvertently rotated from the OA!
I recommend that clinicians consider converting OP presentations to AP prior to traction by one of three methods:1 Digital, using the fingers of the vaginal hand to provide torque on the lambdoid suture of the fetal head;
2 manual, in which the entire hand is inserted into the vagina to cup the head and rotate it; or
3 instrumental, typically with forceps.
A review of patient selection and techniques for rotation is beyond the scope of this article. For more details, see Dennen's Forceps Deliveries, a classic newly republished in a 4th edition by the American College of Obstetricians and Gynecologists, and other similar texts. Note, too, that 'autorotation' can often be observed when appropriate traction is applied to the properly applied vacuum device in OP presentations.
Rotation of the fetal head has been vilified over the years. Yet there is no evidence that rotation per se is to blame for fetal injury in OP presentations. Rather, it may be the injudicious selection of patients for rotation or the persistence of attempted rotation in the face of difficulty that is responsible for fetal injuries. Such rotations are safe if they are accomplished easily in properly selected cases. Similarly, the belief that OP delivery without rotation is safer or better tolerated by the fetus than is a straightforward rotation with delivery as an OA is both contrary to common sense, in my opinion, and unsupported by the evidence.
A systematic review of seven randomized trials of routine versus restricted episiotomy in 5,001 spontaneous vaginal births showed that routine episiotomy was not associated with fewer third-or fourth-degree perineal lacerations in any of the individual studies or overall (six of these seven studies used mediolateral episiotomy as the preferred type).8
It's unclear whether this finding can be extrapolated to operative vaginal delivery because of the absence of prospective randomized trials in this setting. However, a retrospective cohort study of more than 2,000 singleton operative vaginal deliveries, in which almost all episiotomies were mediolateral, showed that episiotomy was associated with a threefold risk of sphincter injury (Table 3).9
To this we can add the retrospective studies cited above, in which a multivariate logistic regression analysis showed that episiotomy increased the odds of a sphincter injury (OR 4.0, 95% CI 1.9–8.4) for vacuum and for forceps (OR 3.1, 95% CI 1.6–5.8).6,7 Other studies have reached similar conclusions.10,11 In contrast, a smaller retrospective Viennese study of 87 patients delivered with forceps linked episiotomy with lower rates of third-degree laceration.12
In a randomized study comparing midline to right mediolateral episiotomy in vaginal birth, sphincter injury occurred in 24% of midline and 9% of medio-lateral episiotomies (P<0.0001), with involvement of the rectal mucosa in 5.5% and 0.4% of cases, respectively (P=0.001).13Among the flaws of this study (conducted by British clinicians with a bias favoring mediolateral episiotomy) was that roughly one fifth of patients assigned to midline episiotomy received the mediolateral type and were not included in the analysis. Forceps were used in about one fifth of the women, but data were not stratified according to that variable.
The absence of a randomized controlled trial of episiotomy in operative vaginal delivery limits the strength of the recommendation, but it seems likely that episiotomy does not reduce higher order perineal lacerations during operative vaginal delivery and may indeed increase their occurrence. The preponderance of evidence further suggests that if episi-otomy is indicated, you should consider creating a mediolateral, rather than a midline incision.
Proper technique is essential for maximizing the chances of successful delivery and for minimizing maternal and neonatal injury with operative vaginal delivery. In the case of forceps, this includes proper application and axis traction. In vacuum deliveries the center of the cup should be placed over the flexion point of the head. (See Dennen's text for forceps and Dr. Aldo Vacca's Handbook of Vacuum Delivery in Obstetric Practice. 2nd edition). With either technique it's important to keep the head flexed during traction to minimize the diameter presenting to the pelvis.
Selecting the proper instrument (for example, a vacuum cup designed specifically for traction on the OP) is essential. I also recommend careful disarticulation of forceps prior to passage of the maximum diameter of the head through the introitus (obviously, this should be timed to occur after successful delivery is assured). Finally, a patient should push only as much as necessary, while the ob/gyn uses the minimal necessary traction when the head is crowning. This can often be accomplished by letting the maximum diameter of the head deliver passively due to the force of a contraction alone, without the addition of maternal or physician effort. Alternatively, the patient can be instructed to push with an open glottis or between contractions.
In our hospital we use a consent form specifically designed for operative vaginal delivery. We find it an excellent educational tool with which to inform patients about the relative risks, benefits, and alternatives ("Consent for operative vaginal delivery"). Except for the rare true emergency, there's almost always time to have a meaningful discussion with patients, similar to the one we conduct prior to moving toward cesarean delivery in labor. Patients appreciate being informed about a procedure they may fear.
In cases where obtaining signed consent is not feasible, the clinician may refer to the content of the consent form as having been covered in the preprocedure discussion. This documentation may prove invaluable for future use in instances where the content of the consent process is in dispute.
Many time-honored practices in obstetrics have been discarded in recent decades, due to their failure to stand up to evidence-based tests of safety and effectiveness. Our specialty can say "good riddance" to most of these (like routine episiotomy and the prophylactic forceps operation). Operative vaginal delivery, however, is one of a smaller number of procedures that appear to be fading away not for this reason, but because of unfounded fear and lack of training. Perhaps a generation from now the operative vaginal delivery-and the forceps operation in particular-will become a historical footnote. Until that day comes, and perhaps to forestall its arrival a little longer, our duty is to do everything possible to minimize its risks.
DR. HIRSCH is Associate Professor of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Ill., and Director, Division of Obstetrics, Evanston Northwestern Healthcare, Evanston, Ill.
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2. Bofill JA, Rust OA, Schorr SJ, et al. A randomized prospective trial of the obstetric forceps versus the M-cup vacuum extractor. Am J Obstet Gynecol. 1996;175:1325-330.
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6. Wu JM, Williams KS, Hundley AF, et al. Occiput posterior fetal head position increases the risk of anal sphincter injury in vacuum-assisted deliveries. Am J ObstetGynecol. 2005;93:525-529.
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13. Coats PM, Chan KK, Wilkins M, et al. A comparison between midline and mediolateral episiotomies. Br J Obstet Gynaecol. 1980;87:408-412.