Understanding and Managing Right Occiput Posterior (ROP) Position in Labor

Rop Position

• Known as the right occipitoposterior position (ROP), this is a commonly encountered malposition.
  • It is more common in nulliparous pregnancies due to tense and tight narrow wall muscles and tight uterine muscles.
  • It is often associated with a narrow anterior pelvis, resulting in more space posteriorly; thus, the head moves to that position. The most common causes of this situation are the android pelvis and anthropoid pelvis.
  • Deflexion of fetal head.
  • High pelvic inclination also favors fetal head deflexion.
  • Anterior placenta. For instance, if the placenta is in the anterior position, then the body curve of the fetus is better aligned posteriorly.

Also read: Preconception Counseling: Optimizing Health for a Successful Pregnancy

Clinical Diagnosis Of Occipital Position

The clinical diagnosis is made on the abdominal and per vaginum examinations

• Abdominal examination:
  • There can be intra-umbilical flattening in place of a bulge.
  • While performing Leonard's maneuvers, the limbs are more easily felt near the midline.
  • The fetal heart sounds are best heard over the flanks (left or right depending on the position).
    • In the occipitoanterior position, the fetal heart sound is transmitted across the fetal backside. In the left occiput anterior position, the fetal heart sounds are heard along the midpoint along the spinoumbilical line near the anterior superior iliac spine.
• Pervaginal examination
• In the well-flexed head position, there is a nice and tense bag of membranes. The head is well applied to the lower uterine segment. When the head is deflexed, there will be an elongated bag of membranes, as the larger diameters are trying to enter the pelvis.
• There is a loose hanging cervix, as the pressure of the bag is absent to help in the dilatation of the cervix effectively.
• The engagement is delayed as the head needs to be flexed, and spontaneous early rupture of membranes can occur.
• To diagnose this position, there should be a thorough assessment of the patient's condition. When the cervix is dilated, the sagittal suture and direction of the posterior fontanelle can be easily felt. However, the anterior fontanelle is easily felt in pervaginal examination in the occipitoposterior position.
  • The sagittal suture is positioned obliquely, and the triangular posterior fontanelle is oriented towards the sacrum in a posterior direction. The anterior fontanelle becomes more accessible due to its anterior placement towards pubic symphysis and head deflection. As a result, the occipitoposterior position can be identified.
• Head deflexion can cause delayed engagement, and there can be early spontaneous rupture of membranes. Also, there can be poor contractions. These can be both causes and effects of head deflection. This is due to the fact that the head can stay deflected, and the ill-fitted head can cause poor contractions. Overall, there is a delayed progression of labor. 

Also read: Physiology Of Lactation : Prolactin Hormone

Labor In Rop

• The head engages through the right oblique diameter of the pelvis. The engaging diameter of the fetal head is suboccipitofrontal or occipitofrontal.
• In 90–95% of cases, there are favorable outcomes. In other words, complete anterior rotation is possible.
  • In the well-flexed head, the suboccipitobregmatic diameter enters the cervix. When the head is deflexed, occipitofrontal diameter enters the pelvis. 
• The head engages through the right oblique diameters of the pelvis from the right sacroiliac joint to the opposite side of iliopubic eminence. 
• With well-coordinated uterine contractions, a favorable pelvis in terms of shape and size, an average-sized baby, and gradual head flexion, the baby's descent progresses, and the head rotates anteriorly. This involves an anterior rotation of the occiput, leading to possible positions like right occipital-transverse with a one-eighth rotation or occipital-anterior with a two-eighths diameter rotation. The shoulders align in the opposite oblique diameter. Subsequently, the head aligns with the pubic symphysis in an occiput-anterior position, exerting one-eighth of tension on the baby's neck. The neck undergoes one-eighth, two-eighths, and three-eighths of the total circle movement, with two-eighths occurring in the same direction as the head's rotation.

• In unfavorable circumstances, like poor contractions and unfavorable shape and size of the maternal pelvis, a big baby, and cardiopulmonary distress, the head fails to flex and there is permanent deflection. This could lead to a halt in labor.
  • In cases of moderate deflexion, where the head is deflected from both the occiput and the sinciput, and they both make contact with the pelvic floor simultaneously, no rotation occurs, and the head remains in an oblique-posterior position. It's worth noting that the occiput typically rotates anteriorly during internal rotation, directing its movement toward the pubic symphysis. This is attributed to the orientation of the fibers in the levator ani muscle, which point downwards and medially. As a result, when only the occiput strikes the pelvic floor, it undergoes internal rotation. However, when both the occiput and the sinciput make contact, head rotation does not occur.
• In cases of severe deflexion, the sinciput strikes the pelvic floor first, and the occiput rotates posteriorly and the sinciput rotates anteriorly. This position is called a direct OP position. The vaginal delivery is possible in this position, provided the pelvis is spacious (either android or gynaecoid). This delivery is called face-to-pubis delivery. The head needs to be flexed first, followed by extension, for delivery of the whole face. 

Also read: Pruritus In Pregnancy : Clinical Presentation

Arrested Occipito Posterior Position 

• The management of the ROP and deep transverse arrest position depends on the stage of labor and the kind of contractions. For example, a deep transverse arrest may be temporary, and with good contractions and good maternal and neonatal health, the doctor can wait for the head to rotate anteriorly.
• Per vaginal examination:
  • In the presence of severe caput, there can be a false sense of station of the head.
  • Position of sagittal suture and occiput to determine the type of arrest.
  • Degree of the deflexion
  • Degree of molding/caput
  • Pelvic adequacy
• In the occipital transverse position, which can be challenging to address, especially during the second stage of labor, the decision to proceed should depend on whether the pelvis is adequate for delivery. Signs of fetal distress, such as asynclitism, severe head molding (grade 3), and the presence of a large caput, should be carefully observed. It's important to note that in cases involving an android pelvis with a narrow forepelvis, there is limited room for anterior rotation. However, in an anthropoid pelvis, the potential for rotation can be anticipated.

• In cases of deep transverse arrest, where labor progress halts at the zero station, manual rotation may be attempted if the pelvis is gynaecoid. However, this approach requires a high level of expertise in performing manual rotation at the zero station. The preferred option in such situations is often a cesarean section.
• In the case of occipitoposterior arrest, vaginal delivery can be considered if the patient has a spacious gynecoid or anthropoid pelvis, experiences strong contractions, and shows no signs or symptoms of cardiopulmonary distress. In some instances, rotation for oblique arrest and the use of rotational forceps have been described as potential interventions. However, due to the need for specialized skills, a cesarean section may still be the chosen approach.
• Clinical identification of the specific circumstances is crucial in these cases. For example, in situations where there is an arrest in the second stage of labor and fetal descent is not occurring, it's important to assess the need for instrumental delivery. However, it's worth noting that in occipitoposterior arrest, forceps-assisted delivery may not always be a feasible option.

Also read: Effective Study Techniques for OBS-GYN Residents

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