20. Dystocia caused by abnormal presentation and position

Question 1

what presentations are considered normal

Answer 1

vertex
occipitoanterior (OA)

all the rest are considered abnormal

Question 2

what is a persistent occipitotransverse position?

Answer 2

the head fails to flex and rotate and persists in an OT position

normally enters and engages in the maternal pelvis in an occipitotransverse (OT) position and then rotates to an occipitoanterior position (85% of cases) or an occipitoposterior position (in 10-15% of cases).

Question 3

why does rotation from OT to OA occur?

Answer 3

because the head flexes as the leading part of the vertex encounters the pelvic floor and then rotates to adjust to the shape of the pelvis.

Question 4

reasons for persistent occipitotransverse position

Answer 4

1) cephalopelvic disproportion
2) altered pelvic architecture (ex. platypelloid or android pelvis)
3) relaxed pelvic floor (ex. epidural anesthesia or multiparity).

Question 5

how do we perform Intrapartum diagnosis of OT position?

Answer 5

1. based on findings on transvaginal digital examination → the fetal sagittal suture and fontanelles are palpable in the transverse diameter of the pelvis.
2. US assessment of the lower abdomen can determine whether or not the face is pointing anterior or posterior, or if the head is flexed or extended.

Question 6

what is transverse arrest and types

Answer 6

Persistent OT position with arrest of descent for ≥ 1 h’
- High transverse arrest – arrest occurs above station +2 (on a -5 cm to +5 cm scale).
- Low (deep) transverse arrest – arrest occurs at or below station +2 (on a -5 cm to +5 cm scale).

Question 7

management of persistent occipitotransverse position

Answer 7

1. Very small fetuses (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.
2. Expectant management is the preferred approach as long as there is some progress in descent over time and the FHR pattern is reassuring. Spontaneous partial or complete rotation may also occur as long as some degree of descent is occurring.
3. An attempt at manual rotation- if a clinician with appropriate expertise is available and the patient consents to the procedure.

*If a clinician with appropriate expertise is not available, the patient is unwilling to undergo the procedure, or the rotation fails → cesarean delivery is generally recommended.

4. In a multiparous patient (‘proven pelvis’) with a fetus in low (deep) transverse arrest → trial of vacuum extraction before cesarean may be attempted.

Question 8

do OP fetuses spontaneously rotate to an anterior position?

Answer 8

yes
during labor, usually just before or during full cervical dilation, leaving only 5-10% of fetuses with a persistent OP position.

Question 9

what is the outcome of persistent OP position?

Answer 9

1. tendency for the second stage to be prolonged (> 2 h’).
2. more discomfort.

*fetuses that remain in the OP position may continue to descend at a reasonable rate and deliver spontaneously from the OP position

Question 10

is manual rotation to the OA position recommended if OP position is diagnosed antepartum, in the first stage of labor, or during the early second stage ?

Answer 10

no
as spontaneous rotation usually follows.

Question 11

what is done in case of women with prolonged second phase and clinically adequate pelvis for rotation (OP position)?

Answer 11

manual rotation to the OA position is superior to expectant management.

Question 12

In case of OP rotation failure, what interventions can be done?

Answer 12

• Forceps assisted delivery from the OP position.
• Vacuum extractor delivery from the OP position.
• Cesarean delivery.

Question 13

diagnosis of OP position is done by?

Answer 13

1. digital vaginal examination in the second stage of labor that identifies the anterior location of the fetal frontal and coronal sutures and anterior fontanelle.
2. In case of uncertainty, US examination can accurately identify fetal head position.