Delivery, Face and Brow Presentation

Anatomy and Physiology

Understanding some anatomical landmarks and their measurements is crucial before discussing the mechanism of labor in the face or brow presentation. 

Planes and Diameters of the Pelvis

The 3 most important planes in the female pelvis are the pelvic inlet, mid-pelvis, and pelvic outlet. Four diameters can describe the pelvic inlet: anteroposterior, transverse, and 2 obliques. Furthermore, based on the landmarks on the pelvic inlet, 3 different anteroposterior diameters named conjugates exist: the true conjugate, obstetrical conjugate, and diagonal conjugate. Only the latter can be measured directly during the obstetric examination. The shortest of these 3 diameters is obstetrical conjugate, which measures approximately 10.5 cm and is the distance between the sacral promontory and 1 cm below the upper border of the symphysis pubis. This measurement is clinically significant as the fetal head must pass through this diameter during the engagement phase. The transverse diameter measures about 13.5 cm and is the widest distance between the innominate line on both sides. The shortest distance in the mid pelvis is the interspinous diameter and usually is only about 10 cm.[8] 

Fetal Skull Diameters

The following are the 6 distinguished longitudinal fetal skull diameters:

• Suboccipitobregmatic: This fetal skull diameter is measured from the center of the anterior fontanelle (bregma) to the occipital protuberance, typically equaling 9.5 cm. This is the diameter presented in the vertex presentation. 
• Suboccipitofrontal: This fetal skull diameter is 10 cm, extending from the anterior part of the bregma to the occipital protuberance.
• Occipitofrontal: The occipitofrontal diameter extends from the root of the nose to the most prominent part of the occiput, measuring 11.5 cm
• Submentobregmatic: This diameter, present in the face presentation where the neck is hyperextended, extends from the center of the bregma to the angle of the mandible, measuring 9.5 cm.
• Submentovertical: This diameter, measuring 11.5 cm, extends from the midpoint between the fontanelles and the angle of the mandible.
• Occipitomental: The occipitomental diameter is the presenting diameter in brow presentation and extends from the midpoint between the fontanelles and the tip of the chin, measuring 13.5 cm.[9]

Cardinal Movements of Normal Labor

Anglo-American literature lists 7 cardinal movements: engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion. German and older English literature lists only 4 rotational movements as the cardinal movements and excludes engagement, descent, and expulsion. Therefore, to define either 4 or 7 is acceptable, with the emphasis on the successful attainment of fetal descent being the primary purpose of these movements, including:

1. Engagement
2. Decent
3. Neck flexion
4. Internal rotation
5. Extension (delivers head)
6. External rotation (restitution)
7. Expulsion (delivery of anterior and posterior shoulders) [10]

Some key movements are impossible in the face or brow presentations.[10][11] Based on the information provided above, it is obvious that labor be arrested in brow presentation unless it spontaneously changes to the face or vertex, as the occipitomental diameter of the fetal head is significantly wider than the smallest diameter of the female pelvis. Face presentation can, however, be delivered vaginally, and further mechanisms of face delivery are explained in later cesarean deliveries.

Indications

As mentioned previously, a spontaneous vaginal delivery can be achieved in face presentation. However, the primary indication for vaginal delivery in such circumstances is maternal preference. Therefore, a thorough conversation with the patient, comparing the risks and benefits of vaginal and cesarean delivery with face presentation, is essential. Clinicians should have supportive and detailed discussions with patients and their family members to obtain informed consent and achieve a safe and successful labor experience.

Contraindications

Vaginal delivery of face presentation is contraindicated if the mentum is lying posteriorly or is in a transverse position. In such a scenario, the fetal brow is pressing against the maternal symphysis pubis, and the short fetal neck, which is already maximally extended, cannot span the surface of the maternal sacrum. In this position, the diameter of the head is larger than the maternal pelvis, and it cannot descend through the birth canal.

Therefore, cesarean delivery is recommended as the safest mode of delivery for mentum posterior face presentations. Attempts to manually convert face presentation to vertex, manual or forceps rotation of the persistent posterior chin to anterior are contraindicated as they can be dangerous. Persistent brow presentation itself is a contraindication for vaginal delivery unless the fetus is significantly small or the maternal pelvis is large.

Equipment

Continuous electronic fetal heart rate monitoring is recommended for face and brow presentations, as heart rate abnormalities are common in these scenarios. One study found that only 14% of the cases with face presentation had no abnormal traces on the cardiotocograph.[12] External transducer devices are advised to prevent damage to the fetal eyes. When internal fetal monitoring is inevitable, monitoring devices on bony parts should be placed carefully. 

Personnel

Consultations that are typically requested for patients with delivery of face or brow presentation include the following:

• Maternal team: The obstetrical team may include experienced midwives, obstetricians, and labor nurses to care for laboring women.
• Neonatal team: These clinicians are focused on attending to neonatal needs following delivery (eg, resuscitation).
• Anesthesiology team: Anesthesiology clinicians are typically necessary to provide pain control (eg, epidural).
• Operating room team: In case of failure to progress, an emergency cesarean delivery is required.

Preparation

No specific preparation is required for face or brow presentation. However, discussing the labor options with the mother and birthing partner before delivery and obtaining consent for the chosen procedure is essential. Additionally, obstetric clinicians should inform and help coordinate neonatal, anesthesiology, and operating room team members.

Technique or Treatment

Mechanism of Labor in Face Presentation

During contractions, the pressure exerted by the fundus of the uterus on the fetus and the pressure of the amniotic fluid initiate descent. During this descent, the fetal neck extends instead of flexing. The internal rotation determines the outcome of delivery. If the fetal chin rotates posteriorly, vaginal delivery would not be possible, and cesarean delivery is permitted. The approach towards mentum-posterior delivery should be individualized, as the cases are rare. Expectant management is acceptable in multiparous patients with small fetuses, as a spontaneous mentum-anterior rotation can occur. However, clinicians should have a low threshold to proceed to cesarean delivery in primigravida patients or those with large fetuses.

The fetus is described as mentum-anterior when the fetal chin is rotated towards the maternal symphysis. In these cases, further descent through the vaginal canal continues, with approximately 73% of cases delivering spontaneously.[13] The fetal mentum presses on the maternal symphysis pubis, and the head is delivered by flexion. The occiput is pointing towards the maternal back, and external rotation occurs. Shoulders are delivered in the same manner as in vertex delivery.

Mechanism of Labor in Brow Presentation

This presentation is considered unstable, as brow presentation is usually spontaneously converted into a face or an occiput presentation. Due to the cephalic diameter being wider than the maternal pelvis, the fetal head cannot engage; thus, brow delivery cannot occur. Unless the fetus is small or the pelvis is very wide, the prognosis for vaginal delivery is poor. With persistent brow presentation, a cesarean delivery is required for safe delivery.

Complications

As cesarean delivery is becoming a more accessible mode of delivery in malpresentation, the incidence of maternal and fetal morbidity and mortality during face presentation has dropped significantly.[14] However, some complications are still associated with the nature of labor in face presentation. Due to the fetal head position, engagement and descent of the head in the birth canal is more difficult, resulting in prolonged labor.

Prolonged labor itself can provoke fetal distress and arrhythmias. If the labor arrests or signs of fetal distress appear on cardiotocography, the recommended next step in management is an emergency cesarean delivery, which in itself carries a myriad of operative and postoperative complications. Finally, due to the nature of the fetal position and prolonged duration of labor in face presentation, neonates develop significant edema of the skull and face. Swelling of the fetal airway may also be present, resulting in respiratory distress after birth and possible intubation. In general, cesarean delivery rates and neonatal intensive care unit admission rates are higher in face and brow presentations compared to cephalic presentation. Additionally, neonatal composite score is also increased in face presentation.[15]

Clinical Significance

During vertex presentation, the fetal head flexes, bringing the chin to the chest, forming the smallest possible fetal head diameter, approximately 9.5 cm. With face and brow presentation, the neck hyperextends, resulting in greater cephalic diameters. As a result, the fetal head engages later, and labor progresses more slowly. Failure to progress in labor is also more common in both presentations compared to the vertex presentation.

Furthermore, when the fetal chin is in a posterior position, further flexion of the fetal neck is prevented, as the fetal brows are pressing on the symphysis pubis. As a result, descending through the birth canal is impossible. Such presentation is considered undeliverable vaginally and requires an emergency cesarean delivery. Manual attempts to change face presentation to vertex or manual or forceps rotation to mentum anterior are considered dangerous and discouraged.[16]

Enhancing Healthcare Team Outcomes

In managing face and brow presentations, an interprofessional team approach is critical for ensuring patient-centered care, safety, and optimal outcomes. Experienced midwives and obstetricians play essential roles in early diagnosis and monitoring, performing detailed vaginal examinations, and assessing fetal positioning to anticipate complications. Sonographers skilled in antenatal scanning contribute valuable expertise, particularly when fetal anomalies like anencephaly or goiter may be factors.

Early involvement of anesthesiologists and neonatal teams is advised, as emergency cesarean delivery and immediate neonatal resuscitation may be necessary. Effective communication and coordinated care among these specialists support timely interventions, minimize risks, and enhance overall team performance in managing complex labor scenarios. By fostering a culture of collaboration, empathy, and shared responsibility, the healthcare team can optimize outcomes, support patient satisfaction, and uphold the standards of patient-centered care.