INTRODUCTION — Occiput transverse (OT) position is a type of fetal cephalic malposition in which the sagittal suture and fontanels align 0 to <15 degrees from the transverse plane of the maternal pelvis (figure 1). Although the position is common before labor begins, most OT fetuses spontaneously rotate during labor as the fetus descends and deliver in the occiput anterior (OA), or less commonly the occiput posterior (OP), position. Persistence of the OT position during labor usually results in 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 — While vaginal digital examination of fetal position is the accepted standard for diagnosis of OT, ultrasound assessment of fetal position can be helpful if the clinical examination is equivocal [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 ultrasound is used to determine fetal position in labor, the obstetric 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, although 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 2A-B). 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. 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. If a transperineal or transvaginal scan is performed, the cerebral midline echo is horizontal or close to horizontal after the head is engaged, as diagramed in the figure (figure 1) [2]. The fetal spine is often lateral, but can also be either anterior or posterior.

Pitfalls in diagnosis — In the setting of OT, anterior or posterior asynclitism, defined as rotation of the sagittal suture away from or toward the pubic symphysis, respectively, may result in misdiagnosis of OT as either occiput anterior (OA) or occiput posterior (OP) if a lambdoid suture is mistaken for the sagittal suture on physical examination. This can be a difficult distinction to make late in labor if there is caput and molding. Determining the position of the ears can help avoid this 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, and both are anterior when the fetus is OP, whereas when only one orbit can be visualized with transabdominal ultrasound, an OT position is likely.

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 delivery 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].

Very small fetuses (eg, very preterm) can deliver in the OT position, but other OT fetuses must rotate anteriorly or posteriorly in order to be able to pass through the maternal pelvic bones and deliver vaginally [10]. Those 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 3). With a platypelloid pelvis, the wide transverse axis of the pelvic inlet readily accommodates the long occipitofrontal diameter (figure 4) 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

Approach to patients without transverse arrest — Expectant management is the preferred approach as long as there is some progress in descent over time and the fetal heart rate pattern is reassuring. Partial or complete rotation may occur spontaneously as long as descent is occurring. Even if manual or forceps rotation or instrumental extraction becomes necessary, it will be easier because of the lower station and/or 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

●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 also more likely to be successful in multiparous patients [13,14]. Whether there is benefit to rotation earlier rather than later during the second stage is unclear. Because there is some risk, albeit small, of umbilical cord prolapse or fetal or maternal injury during rotation, 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. However, slow descent can lead to a prolonged second stage and potentially a more challenging rotation later if descent arrests and the head becomes significantly impacted [14]. In one trial of manual rotation of occiput posterior fetuses, there was a significant reduction in the length of the second stage with early rotation, though no other clinical differences [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 'Manual rotation' below.)

●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.

However, in 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. No attempt to actively rotate the vacuum cup should be made as this can lead to fetal injury.

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 studies are not available. (See 'Vacuum extraction' below.)

●Role of forceps – For the fetus in 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). We would attempt manual rotation first because it is technically easier and less morbid than forceps rotation.

It is now rare for physicians to have the requisite experience needed to safely and effectively attempt forceps rotation of the fetus in high transverse arrest. Such physicians may consider forceps rotation and fetal extraction under extreme circumstances, such as the sudden onset of severe fetal or maternal compromise.

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 "Operative vaginal delivery", section on 'Prerequisites'.)

Maneuvers

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

Manual rotation — Manual rotation can be 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 rotating it between contractions via rotation of the operator's hand and forearm. Ideally, rotation is toward the OA position. Alternatively, the operator's thumb and fingers can be placed on the parietal bones to grasp the head, which is then rotated. There are no randomized trials comparing these techniques, so physicians should become comfortable performing either or both techniques.

After manual 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.

The effectiveness of manual rotation is supported by a retrospective cohort study that found that patients with fetuses in OT or occiput posterior positions who had a trial of manual rotation in the second stage (n = 731) had a 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) [16]. However, the intervention was associated with an increased risk of cervical laceration (2.2 versus 1.0 percent). Because of this risk, we prefer expectant management to manual rotation as long as labor is progressing and the fetal heart rate is normal.

Vacuum extraction — Persistent OT position occurs infrequently, and the performance of even easy forceps deliveries in the United States is diminishing; thus, many clinicians lack the training, experience, and sound clinical judgment that come with 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 [17].

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 [18]. A flexible stem permits placement and movement of the device within the limited space of the vagina [19]. Anterior autorotation is most likely to occur when cup application and traction result in head flexion rather than deflexion [20-22]. The vacuum extractor itself should not be manipulated to rotate the head. (See "Procedure for vacuum-assisted vaginal delivery".)

Forceps rotation — 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 [23,24]; 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 lead to injury of the birth canal 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

●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 2B). 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.)

●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). If a transperineal or transvaginal scan is performed, the cerebral midline echo is horizontal or close to horizontal after the head is engaged (figure 1). (See 'Diagnostic findings on ultrasound examination' above.)

●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.)

●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:

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

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

(See 'Clinical course' above and 'Pitfalls in diagnosis' above.)

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

●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.

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 delivery is generally performed.

However, in a multiparous patient (ie, "proven pelvis") with a fetus in 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. (See 'Approach to patients with transverse arrest' above.)

●For the fetus in 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. (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.