Rotational forceps delivery. During residency I was told to always use rotational forceps to deliver a fetus in the persistently OP position if the parturient had a gynecoid pelvis (wide oval shape of pelvic bones, wide subpubic arch). Dr. Frederick Irving wrote16:
“Although textbooks almost universally advocate the extraction of the occiput directly posterior without rotation we do not advise it.... Such an extraction maneuver is inartistic and show[s] a lack of regard for the mechanical factors involved in the mechanism of labor. The method used at the Boston Lying-In Hospital presupposes an accurate diagnosis of the primary position. If the fetal back is on the right the head should be rotated to the right; if on the left, toward the left. The head is always rotated in the direction in which the back lies. The forceps are applied as if the occiput was directly anterior. Carrying the forceps handles in a wide sweep the occiput is now rotated to the anterior quadrant of the pelvis or 135 degrees. It will be found that the head turns easily in the way it should go but that it is difficult or impossible to rotate it in the improper direction. The instrument is then reapplied as in the second part of the Scanzoni maneuver.”
Rotation of the fetus from the OP to the OA position may reduce the risk of sphincter injury with vaginal birth. With the waning of rotational forceps skills, many obstetricians prefer a nonrotational approach with direct forceps or vacuum delivery from the OP position.
Direct forceps delivery from the OP position. A fetus in the OP position for 3 to 4 hours of the second stage of labor will often have a significant degree of head molding. The Simpson forceps, with its shallow and longer cephalic curve, accommodates significant fetal head molding and is a good forceps choice in this situation.
Vacuum delivery. In the United States, approximately 5% of vaginal deliveries are performed with a vacuum device, and 1% with forceps.17 Consequently, many obstetricians frequently perform operative vaginal delivery with a vacuum device and infrequently or never perform operative vaginal delivery with forceps. Vacuum vaginal delivery may be the instrument of choice for many obstetricians performing an operative delivery of a fetus in the OP position. However, the vacuum has a higher rate of failure, especially if the OP fetus is at a higher station.18
In some centers, direct forceps delivery from the OP position is preferred over an attempt at vacuum delivery, because in contemporary obstetric practice most centers do not permit the sequential use of vacuum followed by forceps (due to the higher rate of fetal trauma of combination operative delivery). Since vacuum delivery of the fetus in the OP position has a greater rate of failure than forceps, it may be best to initiate operative vaginal delivery of the fetus in the OP position with forceps. If vacuum is used to attempt a vaginal delivery and fails due to too many pop-offs, a CD would be the next step.
Take action when needed to optimize outcomes
The persistent OP position is associated with a longer second stage of labor. It is common during a change of shift for an obstetrician to sign out to the on-coming clinician a case of a prolonged second stage with the fetus in the OP position. In this situation, the on-coming clinician cannot wait hour after hour after hour hoping for a spontaneous delivery. If the on-coming clinician has a clear plan of how to deal with the persistent OP position—including ultrasound confirmation of position and physical examination to determine station, fetal size and adequacy of the pelvis, and timely selection of a delivery technique—the adverse maternal and neonatal outcomes sometimes caused by the persistent OP position will be minimized.
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