The occiput posterior (OP) and occiput transverse (OT) positions of the fetus in labor pose a notorious clinical challenge. (Throughout this chapter, whenever OP position is addressed, the reader should assume the inference of OT positions similarly.) Approximately 15% to 20% of fetuses present in labor in the OP position, and most of those rotate spontaneously. Roughly 5% remain OP. The right occiput posterior (ROP) position is two to five times more common than left occiput posterior (LOP), which is thought to be due to a combination of dextrorotation of the uterus, bladder in the right anterior and rectum in the left posterior portions of the maternal pelvis, and the dense liver on the right side of the fetus.

Occiput posterior positions are thought to account for 25% of all primary cesarean sections (C-sections). In the United States, nine of ten women who have had a primary C-section will have subsequent cesarean deliveries. Several studies demonstrate the effectiveness of manual rotation to increase rates of vaginal delivery in the setting of OP or OT fetal positions.^1–3 The American College of Obstetricians and Gynecologists (ACOG), in concert with the Society for Maternal-Fetal Medicine (SMFM), released a joint Obstetric Care Consensus in 2014 on Safe Prevention of the Primary Cesarean Delivery.⁴ Prior to a decision for C-section or operative vaginal delivery, a trial of manual rotation of the OP vertex in the second stage is suggested as a reasonable alternative. The Society of Obstetricians and Gynecologists of Canada similarly endorses manual rotations, as does the American Academy of Family Physicians’ Advanced Life-Saving Skills in Obstetrics (ALSO) course.^5,6 Despite these recommendations, many obstetricians do not routinely offer manual rotation of the OP or OT fetus to their laboring patients. The OB/GYN hospitalist, therefore, may be able to affect the primary C-section rate directly by offering to perform and/or train others in these maneuvers.

In order to utilize the space in the posterior pelvis, an OP fetus must, of necessity, cross the pelvic brim in a deflexed position, presenting the longer occipito-frontal diameter (Fig. 66-1). Concurrent asynclitism is common. There is misaligned axis pressure of the fetal body exerted through the pelvis, placing added pressure upon the sacral nerves and asymmetric pressure on the cervix. (Fig. 66-2). The pressure of an asymmetrically applied and often irregularly shaped fetal head also predisposes to early rupture of membranes.

FINDINGS ASSOCIATED WITH OCCIPUT POSTERIOR LABORS

The labor pattern with an OP fetus may exhibit any number of characteristic physical features. On exam, Leopold’s maneuvers find multiple fetal small parts in front, and the fetal heart tones are heard either centrally or far lateral. When viewed in profile, a scaphoid curvature to the maternal low abdomen may be noted (Fig. 66-3). Cervical examination reveals the large anterior fontanelle within the anterior semicircle of the cervix or just beyond its borders under the symphysis, and the posterior fontanelle posteriorly. As OP labors progress, the development of caput is common, which in turn obscures the cranial landmarks from below. There is asymmetrical dilatation of the cervix, cervical edema, or a persistent anterior lip of cervix. Coupled or tripled contractions are characteristic, leading to a labor pattern that may be protracted in any or all phases. Variable decelerations with contractions are more common. Maternal symptoms include report of fetal kicks felt near the umbilicus, back pain, physical and emotional exhaustion, and an early urge to push caused by pressure of the occiput on the sacral nerves.

PROBLEMS ASSOCIATED WITH OCCIPUT POSTERIOR LABORS

For the mother, OP fetal position makes for greater risks of induction for postdatism, oxytocin augmentation of labor, prolonged first and second stages, chorioamnionitis, epidural use, operative vaginal delivery, failed operative vaginal delivery, C-section, third- and fourth-degree perineal lacerations (independent of the use of vacuum or forceps), higher estimated blood loss, postpartum hemorrhage (PPH), and postpartum infection.⁷

For the babies, OP position makes for greater risk of variable FHR decelerations, Apgar scores <7, meconium-stained amniotic fluid, acidemic cord blood gases, birth trauma, neonatal intensive care unit (NICU) admissions, and longer hospital stays.⁸

PREDISPOSING FACTORS

Maternal phenotypical characteristics encouraging OP position include android- or anthropoid-type pelvis, flat sacrum, anterior placenta, lax abdominal musculature or pendulous abdomen, and short stature. Fetal OP positioning is also more common in nulliparas, with maternal age >35, obesity, history of OP positioning of a prior fetus, gestational age >41 weeks, or birth weight >4000 g.⁷ Given the recognized association of OP positioning with gestational age beyond 41 weeks or birth weight >4000 g, inclusion of the greater risk of OP labor might reasonably be included in informed consent related to induction.

THE ROLE OF EPIDURAL ANESTHESIA IN OCCIPUT POSTERIOR POSITIONING

Regional anesthesia may be a factor associated with fetal OP positioning in labor. Obstetricians began publishing this observation with the advent of caudal analgesia in the 1940s. In a prospective cohort study from Brigham and Women’s Hospital published in 2005, 1562 nulliparas had fetal position determined by ultrasound at enrollment, at the time of epidural administration (or 4 hours after enrollment if no epidural), and late in labor at >8 cm dilatation. Fetal position at birth was reported by delivering providers. Patients electing epidural anesthesia had no more fetuses in the OP position at enrollment or at the time of epidural placement. However, in the epidural group significantly more fetuses were in the OP position at the time of delivery (12.9% vs. 3.2%, P = .002). The association remained in a multivariate model [adjusted odds ratio (OR) 4.0, 95% confidence interval (CI) 1.4–11.1].⁹ Relaxation of the muscles of the pelvic floor is the likely mechanism for the failure of internal rotation to the occipital anterior (OA) position.

THE POSSIBLE ROLE OF ARTIFICIAL RUPTURE OF MEMBRANES IN OCCIPUT POSTERIOR POSITIONING

In a large, retrospective cohort study, artificial rupture of membranes (AROM) was statistically significantly associated with persistent OP position, including in multivariate logistic regression analysis, controlling for prolonged labor, induction, and augmentation.⁷ Given this finding, and the logical inference that fetal mobility might benefit from the increased buoyancy and decreased friction of intact membranes, in a labor characterized by OP or OT position, avoidance of AROM might reasonably be considered.

Since the OP position is relatively common at some point during normal labor, and most OP fetuses will rotate spontaneously, not all fetuses incidentally noted to be in the OP position should have an attempted rotation performed. Indications for manual rotation of an OP or OT fetus are listed in Box 66-1. In general, rotation from an OP position should be considered when the OP position of the fetus is persistent, the patient’s labor is protracted, and/or an expeditious delivery is required (typically for fetal indications).

Contraindications to manual rotation include heavy vaginal bleeding; known, palpable, compound presenting part; cord prolapse; or maternal or fetal blood dyscrasia. Having a prior C-section is not a contraindication to manual rotation.

Informed consent for manual rotation should include a full description of the procedure, the alternatives to intervention with manual rotation, and the possible risks (Table 66-1). Risks of attempted manual rotation for the mother include increased discomfort during the procedure and increased risk of cervical laceration (2.2% in the rotation group, without concurrent PPH, as opposed to 1.0% in the expectant group in a large, retrospective cohort study).³ Risks for the fetus include hypothetical neck injury with malrotation, cord entrapment or prolapse (especially if destationing the fetal head prior to rotation), and FHR changes during some rotations. The largest study to date reported that 71% of cases of attempted rotation showed no abnormality of FHR, 19% showed mild or moderate FHR abnormalities, and 10% showed severe FHR abnormalities. No association was found between FHR abnormality after manual rotation and cesarean delivery.¹ The risk of bleeding in the setting of maternal idiopathic thrombocytopenia (ITP) or fetal neonatal alloimmune thrombocytopenia (NAIT) is the contraindication to manual rotation in those patients.