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Occiput transverse position

Occiput transverse position
Literature review current through: Jan 2024.
This topic last updated: Jun 06, 2023.

INTRODUCTION — The large majority of fetuses in active labor and the second stage are in the occiput anterior (OA) position, but a small proportion experience malposition with occiput posterior (OP) or occiput transverse (OT). OT position is a fetal cephalic malposition in which the sagittal suture and fontanels align 0 to <15 degrees from the transverse plane of the maternal pelvis (figure 1A). Although the position is common before labor begins, most OT fetuses spontaneously rotate as the fetus descends along the birth canal during labor and deliver in the OA, or less commonly the occiput posteriorOP, position. Persistence of the OT position in the second stage of labor usually results in labor protraction or arrest of descent, necessitating iatrogenic rotation or cesarean birth.

This topic will discuss the diagnosis, clinical course, and management of OT position. OT position is unrelated to transverse lie, in which the long axis of the fetal body is perpendicular to the long axis of the mother. (See "Transverse fetal lie".)

PREVALENCE — Up to 50 percent of fetuses are OT at the onset of labor, but the prevalence falls to 19 to 20 percent in the second stage and 3 to 8 percent at the time of delivery [1].

DIAGNOSIS — Vaginal digital examination of fetal position is the accepted standard for diagnosis of OT and is accurate because the sagittal suture is relatively easy to identify. In settings where digital examination is equivocal, ultrasound assessment of fetal position can be helpful [2]. Either transvaginal, transperineal, or transabdominal ultrasound examination can be performed, though the transvaginal and transperineal approaches tend to provide clearer images when the head is at a low station because shadowing from the maternal bony pelvis is eliminated [3-6].

If an obstetrical provider uses ultrasound to determine fetal position in labor, the provider should receive specialized training for this type of sonographic examination and undergo supervision by a more experienced diagnostician until they develop proficiency. The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) has an online video that provides guidance on techniques and sonographic findings.

Diagnostic findings on digital examination — Intrapartum diagnosis of OT is generally based on findings from the transvaginal digital examination, which is modestly less accurate than ultrasound-based diagnosis. The fetal sagittal suture and fontanelles are palpable in the transverse diameter of the pelvis. One fetal ear can be palpated superiorly under the symphysis and the other inferiorly above the sacrum/coccyx.

If the occiput (posterior fontanelle) is on the mother's left side, the position is left OT (LOT); if the occiput (posterior fontanelle) is on the mother's right side, the position is right OT (ROT) (figure 1A-C). LOT is more common than ROT.

Diagnostic findings on ultrasound examination — The key diagnostic feature for identification of OT position is the location of the fetal orbits: one orbit is anterior and the other is posterior (though commonly only the anterior orbit can be seen). If both orbits are on the maternal left, then the fetal position is ROT. If both orbits are on the maternal right, then the position is LOT. The cerebral midline echo is horizontal or close to horizontal after the head is engaged, as diagramed in the figure (figure 1A) [2]. The fetal spine is often lateral, but can also be either anterior or posterior. Using a combination of transabdominal and transperineal ultrasound provides the clearest images of midline structures of the fetal head at low stations.

Pitfalls in diagnosis — In cases of OT with anterior or posterior asynclitism (rotation of the sagittal suture away from or toward the pubic symphysis), the lambdoid suture may be mistaken for the sagittal suture on physical examination and lead to an erroneous diagnosis of either occiput anterior (OA) or occiput posterior (OP). This generally happens late in labor when caput and molding are present. Determining the position of the ears can help avoid misdiagnosis: The fetus is OT if an ear is palpated underneath the pubic symphysis at 12 o'clock and another is palpable at 6 o'clock. If the fetal ears are palpated at 3 o'clock and 9 o'clock, then the fetus is OA or OP.

Ultrasound examination can also be used to clarify the fetal position [7,8]. Both orbits are posterior when the fetus is OA, both are anterior when the fetus is OP, whereas one is anterior and one is posterior with OT.

CLINICAL COURSE — During the course of labor, approximately 80 percent of fetuses in the OT position rotate anteriorly to the occiput anterior (OA) position, approximately 10 to 15 percent rotate posteriorly to the occiput posterior (OP) position, and the remainder remain OT [9]. The frequency of OT at birth appears to be similar in patients with and without neuraxial anesthesia, in contrast to OP position, which appears to be more likely to persist in patients with neuraxial anesthesia [9].

The widest dimension of the pelvic inlet is its transverse diameter so most fetus are OT as they pass through the inlet. Although very small fetuses can maintain an OT position, other OT fetuses must rotate anteriorly or posteriorly to deliver vaginally because the widest diameter of the pelvic outlet is its anteroposterior diameter [10]. Fetuses that do not rotate and descend after at least two hours of active pushing can be divided into two subsets [11]:

High transverse arrest – Arrest above station +2 (on a -5 cm to +5 cm scale)

Low (deep) transverse arrest – Arrest at or below station +2 (on a -5 cm to +5 cm scale)

Transverse arrest is thought to result from constraint to rotation by the bony pelvis and/or inadequate power to induce rotation from contractions or maternal expulsive efforts [12]. Although transverse arrest can occur with any pelvic type, it is more common with the platypelloid (flat) or android pelvis (figure 2). With a platypelloid pelvis, the wide transverse axis of the pelvic inlet readily accommodates the long occipitofrontal diameter (figure 3) of the fetal head as it enters the pelvis, resulting in OT position; however, there may be inadequate room in the midpelvis to allow continuous descent in the OT position; natural rotation to OA or OP is also impeded. Similarly, the pelvic inlet of the android pelvis initially readily accommodates the head in OT position, but deep descent and natural rotation to OA or OP are impeded by the forward inclination of the sacrum.

Transverse arrest can also result from inadequate uterine expulsive forces because these forces normally facilitate rotation from the OT to the OA position.

MANAGEMENT IN THE SECOND STAGE

Approach to patients without transverse arrest — At the beginning of the second stage, we prefer expectant management to manual rotation as long as there is some descent over time and the fetal heart rate pattern is reassuring, given the lack of strong evidence for improved outcomes and the potential for harm with intervention. However, others may choose to perform a prophylactic rotation in the second stage when the OT position is identified.

Because maternal expulsive efforts increase the force on the fetal head, partial or complete rotation may occur spontaneously as long as descent is occurring. If progress stops during the course of the second stage, that is the time when we consider performing manual rotation. Whether the outcome is better with rotation earlier rather than later during the second stage is unclear. Because rotation has some risk, albeit small, of umbilical cord prolapse or fetal or maternal injury, usual practice is a period of expectant management to see if rotation occurs on its own during the second stage, especially when descent is occurring. Although not performing a manual rotation can lengthen the second stage [13] and result in a potentially more challenging rotation if the head becomes significantly impacted [14], expectant management can also result in an easier extraction if descent progresses to a lower station and/or the head rotates to a nontransverse position.

Protraction associated with hypocontractile uterine activity is treated with oxytocin augmentation, as in any pregnancy. (See "Labor: Overview of normal and abnormal progression", section on 'Hypocontractile uterine activity' and "Labor: Diagnosis and management of an abnormal first stage", section on 'Oxytocin and amniotomy' and "Labor: Diagnosis and management of a prolonged second stage".)

Approach to patients with transverse arrest

Role of manual rotation – An attempt at manual rotation is reasonable if a clinician with appropriate expertise is available and the patient consents to the procedure. It is more likely to be successful in multiparous patients [14,15]. Manual rotation may succeed when natural autorotation fails to occur because the combination of slight dislodgement and iatrogenic flexion of the head coupled with iatrogenic rotational force may remove previous barriers to autorotation. (See 'Digital/manual rotation' below.)

Vacuum- or forceps-assisted delivery can be considered after a failed manual rotation and before cesarean in specific circumstances.

For multiparous patients (ie, "proven pelvis") with a low (deep) transverse arrest, we believe a trial of vacuum extraction is reasonable if manual rotation fails. When the vacuum cup is placed at the median flexion point (ie, pivot point 3 cm anterior to the posterior fontanelle), downward traction can facilitate autorotation of the fetus to the occiput anterior (OA) position as descent occurs. Actively rotating the vacuum cup can lead to fetal injury and should be avoided. (See 'Vacuum extraction' below.)

We would not attempt a trial of vacuum extraction in nulliparous patients or patients with high transverse arrest because the risk for failure and/or morbidity is probably high, although data from randomized trials or large cohort or case-control studies are not available.

For patients with low (deep) transverse arrest, forceps rotation is a reasonable second-line option after failed manual rotation if a clinician with appropriate expertise is available and the patient consents to the procedure (see 'Forceps rotation' below). The standard prerequisites for forceps delivery should be met (eg, cervix is fully dilated, head is engaged, membranes are ruptured, fetal position is known, pelvis is adequate, patient consents). (See "Assisted (operative) vaginal birth", section on 'Prerequisites'.)

For patients with high transverse arrest, forceps rotation is no longer performed. It is now rare for physicians to have the requisite experience needed to safely and effectively attempt forceps rotation in this setting. These few physicians may consider forceps rotation and fetal extraction under extreme circumstances, such as the sudden onset of severe fetal or maternal compromise.

Role of cesarean birth – If a clinician with appropriate expertise at manual rotation is not available, the patient is unwilling to undergo the procedure, or the rotation fails, then a cesarean birth is generally recommended, based on clinical experience and expert opinion. Vacuum- or forceps-assisted delivery can be considered after a failed manual rotation and before cesarean in the specific circumstances described above.

Maneuvers

Preparation — When a manual or forceps rotation is attempted, preparations for a cesarean birth should be made concurrently. Both of these rotation interventions require elevating (disengaging) the head into the midpelvis to facilitate rotation. As such, the risk for cord prolapse is increased during the maneuver. (See "Umbilical cord prolapse".)

Digital/manual rotation — Digital rotation to the OA position is performed by grasping the fetal head with the operator's hand, placing the tips of the index and middle fingers along the lambdoid sutures, dislodging the head into the midpelvis, flexing it, and then using the finger tips to rotate it between contractions via rotation of the operator's hand and forearm. Manual rotation is performed by placing the operator's thumb and fingers on the parietal bones to grasp the head, and then the entire hand is used for the rotation. Manual rotation may be slightly more successful than digital rotation [16].

After rotation, holding the head in position for a few contractions can help to prevent rotation back toward the transverse position. The mother should push during the contractions to facilitate descent of the now-rotated head and thus improve the chances that it will remain in OA position.

Two meta-analyses of small randomized trials have assessed the utility of digital/manual rotation of malposition.

The first compared prophylactic manual rotation with either no rotation or a sham rotation procedure in the second stage in pregnancies in which OP and OT malpositions were confirmed using ultrasound examination (6 randomized trials, 1002 patients) [17]. Major findings were:

Manual rotation did not result in a clear difference in the rate of spontaneous vaginal birth (relative risk [RR] 1.07, 95% CI 0.95-1.20) or any other maternal or fetal outcome.

In a subgroup analysis of OP fetuses, manual rotation reduced the length of the second stage by approximately 13 minutes (95% CI -23 to -3).

The second meta-analysis was similar (7 randomized trials, 1402 participants) [16]. Major findings were:

Manual rotation slightly increased the rate of spontaneous vaginal birth in the overall group (RR 1.09, 95% CI 1.03-1.16) but the result was no longer statistically significant after stratification by parity or technique used, or for OT position when OT and OP positions were analyzed separately.

Although OT and OP malpositions at delivery were reduced, this did not lead to statistically significant differences in cesarean or operative vaginal birth rates or neonatal outcomes.

In contrast, a large retrospective cohort study found that patients with fetuses in OT or OP positions who had a trial of manual rotation in the second stage (n = 731) had a substantially lower risk of cesarean birth (adjusted odds ratio 0.12, 95% CI 0.09-0.16) than those who did not have a trial of manual rotation (n = 2527) [18]. The intervention was associated with an increased risk of cervical laceration (2.2 versus 1.0 percent).

Vacuum extraction — Persistent OT position occurs infrequently, and the performance of forceps-assisted deliveries in the United States is diminishing; thus, many clinicians lack the training and experience to perform a 90-degree forceps rotation. In the United States, vacuum is used four- to fivefold more often than forceps for assisted vaginal delivery [19].

Although rotational force or torque should never be applied when pulling on the vacuum extractor, the downward/outward force on the fetal head may lead to an autorotation from OT to OA position during extraction. Proper cup placement is essential, and selection of an appropriate cup design for the clinical situation is important. A rigid vacuum cup is advantageous over a soft cup because it allows greater traction, which is often needed for autorotation from OT [20]. A flexible stem permits placement and movement of the device within the limited space of the vagina [21]. Anterior autorotation is most likely to occur when cup application and traction result in head flexion rather than deflexion [22-24]. The vacuum extractor itself should not be manipulated to rotate the head. (See "Procedure for vacuum-assisted vaginal birth".)

Forceps rotation — While far fewer clinicians in the United States are being trained in forceps rotation, it is still a valuable approach worldwide for the persistent OT position. Kielland forceps were specifically designed without a pelvic curve and with a sliding lock to improve performance of rotational procedures. The toes, blades, shanks, and handle lie along the long axis, so the toes travel along a smaller circle during rotation than with conventional forceps. Some authors have reported high success and low morbidity rates with use of these forceps [25,26]; however, their use is best avoided in the rare case of a platypelloid pelvis.

Conventional forceps (eg, Simpson or Tucker-McLane) can be used for rotation, but the pelvic curve of such forceps makes the technique more difficult and may increase the risk of injury of the birth canal, particularly if the operator is not sufficiently experienced.

Technical considerations regarding choice of forceps, as well as application, rotation, and traction, are complex and beyond the scope of this topic review.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Labor".)

SUMMARY AND RECOMMENDATIONS

Physical examination – Intrapartum diagnosis of occiput transverse (OT) position is generally based on findings on transvaginal digital examination: The fetal sagittal suture and fontanelles are palpable in the transverse diameter of the pelvis (figure 1C). One fetal ear can be palpated superiorly under the symphysis and the other inferiorly above the sacrum/coccyx. (See 'Diagnostic findings on digital examination' above.)

Sonographic diagnosis – On ultrasound examination, the key diagnostic feature is the location of the fetal orbits: One orbit is anterior, and the other is posterior. If both orbits are on the maternal left, then the fetal position is right OT (ROT). If both orbits are on the maternal right, then the position is left OT (LOT). The cerebral midline echo is horizontal or close to horizontal after the head is engaged (figure 1A). (See 'Diagnostic findings on ultrasound examination' above.)

Natural history – As the fetus descends along the birth canal during the course of labor, approximately 80 percent of those in the OT position rotate anteriorly (internal rotation) to the occiput anterior (OA) position, approximately 10 to 15 percent rotate posteriorly to the occiput posterior (OP) position, and the remainder remain OT. (See 'Clinical course' above.)

Pathogenesis – Persistent OT position results from either constraint to rotation to an anterior or posterior position by the bony pelvis or inadequate power (ie, uterine contractions, maternal pushing). Arrest of descent is the major consequence and is defined as (see 'Clinical course' above and 'Pitfalls in diagnosis' above):

High transverse arrest – Arrest above station +2 (on a -5 cm to +5 cm scale)

Low (deep) transverse arrest – Arrest at or below station +2 (on a -5 cm to +5 cm scale)

Management when descent is occurring For management of OT position with progressive descent, we suggest expectant management rather than prophylactic digital/manual rotation (Grade 2C). If hypocontractile uterine activity is present, contractions should be augmented with oxytocin. (See 'Approach to patients without transverse arrest' above.)

Management when descent is not occurring

Role of manual rotation – For management of transverse arrest, an attempt at manual rotation is a reasonable option if a clinician with appropriate expertise is available and the patient consents to the procedure. It is best to attempt the rotation soon after diagnosis of the arrest because it is more likely to be successful before the head becomes significantly impacted in pelvis. (See 'Approach to patients with transverse arrest' above.)

Vacuum- or forceps-assisted delivery can be considered after a failed manual rotation and before cesarean in specific circumstances. (See 'Approach to patients with transverse arrest' above.)

-For a multiparous patient (ie, "proven pelvis") with a low (deep) transverse arrest, a trial of vacuum extraction before cesarean is a reasonable approach if the patient consents to the procedure. Vacuum extraction may result in autorotation and thus enable subsequent extraction.

-For the patient with a low (deep) transverse arrest, forceps rotation is a reasonable option after failed manual rotation if a clinician with appropriate expertise is available (which is rare) and the patient consents to the procedure. In high transverse arrest, forceps rotation is almost always contraindicated because of the high risk of maternal and fetal morbidity.

Role of cesarean birth – If a clinician with appropriate expertise for manual rotation is unavailable or the patient is unwilling to undergo manual rotation or the attempt at rotation fails, cesarean birth is generally performed. Vacuum- or forceps-assisted delivery can be considered after a failed manual rotation and before cesarean in the specific circumstances described above. (See 'Approach to patients with transverse arrest' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Dr. Edward R Yeomans and Dr. Clint M Cormier, who contributed to earlier versions of this topic review.

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