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This forceps-aided rotation can be used when the fetus is occiput posterior and the head is low in the pelvis.
Your patient has had a long, slow labor, with pain predominantly in her back (the infamous "back labor"). She is now fully dilated and the head has progressed well into the pelvis, but it is not crowning, and you find that the patient's exam is notable for right occiput posterior (OP) position. The patient is exhausted. She has tried a number of physical maneuvers and labor positions with minimal progress. Manual rotation of the head was unsuccessful. The choice at this point is to move to a cesarean delivery or to try a Scanzoni rotation to turn the head with forceps with physicians aiding the rotation abdominally. A cesarean delivery is less desirable in this case as the head is wedged down deep in the pelvis.
The Scanzoni maneuver was invented by Friedrich Wilhelm Scanzoni, a German obstetrician, in 1849. His method for changing a posterior presentation into an anterior one required the use of forceps twice in the process of delivery.1
OP positions are the most common type of malposition, cited to comprise between 1% and 5%.2 They are often accompanied by some degree of deflexion, resulting in a larger presenting diameter. The presence of asynclitism and molding can make it difficult to correctly determine position, leading to an inaccurate diagnosis of occiput anterior (Figure 1). Risk factors for OP position include smaller pelvic outlet capacity, prior OP, nulliparity, maternal age >35, gestational age ≥41 weeks, birth weight >4000 g, artificial rupture of the membranes (AROM), and epidural anesthesia.3 OP position as a cause for persistent labor dystocia can be corrected using the Scanzoni method, allowing successful vaginal delivery.
All illustrations by Alex Baker, DNA Illustrations, Inc.
Our preferred forceps to use for Scanzoni rotation are Tucker-McLane, in this case with the Luikart modification. Tucker-McLane forceps feature solid rather than fenestrated blades. The Luikart modification is a pseudofenestration. Most importantly, unlike the Simpson forceps blades with their widely separated shanks, the shanks of the Tucker-McLane forceps are overlapping. This decreases the risk of a tear during the wide rotation when correcting the position of the head. An article by W Barth, MD, recently published in Obstetrics & Gynecology, described rotational forceps using the Kielland forceps followed by Simpson forceps for traction and delivery.4 We find that the Scanzoni maneuver is preferable to facilitate successful delivery of a persistently OP baby. We favor the solid pseudofenestrated blades of the Tucker-McLane forceps with Luikart modification for ease of application and find that they result in fewer injuries to the fetal facial skin.
For successful completion of the Scanzoni maneuver, the patient should be in the dorsal lithotomy position. To begin, the forceps are applied to the head in the usual fashion, with the posterior blade placed first, and the anterior blade second. The blades should be oriented with their pelvic curve aligned to the curve of the maternal sacrum, as with any forceps placement. The blades are then articulated so that they overlap and the handles squeezed together to lock the blades in place around the head which corrects the asynclitism (Figure 2A).
All illustrations by Alex Baker, DNA Illustrations, Inc.
The next portion of this maneuver is initiated by using the forceps to flex the fetal neck and dislodge the malpresenting cranium. The shanks of the forceps should be directed in a wide arc beginning between 12- and 3-o’clock, and ending at 6 o’clock, essentially "screwing out" the head with the natural forces of contraction as well as laterally directed pressure on the abdomen applied by an assistant (Figure 2B 1,2).
The lateral pressure serves to rotate the shoulder simultaneously with the head. The angle of the shanks in relation to the maternal spine is crucial. The shanks should be oriented almost vertically, perpendicular to the maternal spine, almost parallel to the maternal thighs in the dorsal lithotomy position. It is this wide angle that gives the operator an appropriate amount of torque and more importantly, maintains flexion of the fetal neck throughout rotation. Once rotation is complete, the blades must be switched in order to realign them with the maternal pelvic curve. This is easiest if done between contractions (Figure 2C). Removal and replacement of the forceps should be done following the curve of the blades, as in any forceps maneuver. The blade that is now posterior can be removed and replaced inside the anterior blade. The anterior blade is then removed and replaced posteriorly. Keeping one blade in place at all times will splint the head in its rotated position, preventing reversal of rotational progress.
Finally, the forceps can be rearticulated and used to guide the head out to crowning station (Figure 2D). At this point the blades should be removed and the head and body delivered with maternal effort to avoid unnecessary trauma to the perineum. Management of the third stage of labor can proceed in a standard fashion.
Illustrations by Alex Baker, DNA Illustrations, Inc.
1. Merriam-Webster.com. Scanzoni Maneuver. http://www.merriam-webster.com/medical/scanzoni%20maneuver. Accessed April 20, 2015.
2. Sizer AR, Nirmal DM. Occipitoposterior position: associated factors and obstetric outcome in nulliparas. Obstet Gynecol. 2000;96(5):749–752.
3. Cheng YW, Shaffer BL, Caughey AB. Associated factors and outcomes of persistent occiput posterior position: A retrospective cohort study from 1976 to 2001. J Matern Fetal Neonatal Med. t in2006;19(9):563–568.
4. Barth W. Persistent occiput posterior. Obstet Gynecol. 2015;125(3):695–709.