Lecture 18: Dysf. Labor Uterine Contractility and Dystocia

Question 1

During labor, 2 distinct segments of the uterus are formed, what is the function of each?

Answer 1

• Upper segment: actively contracts and retracts to expel fetus
• Lower segment: becomes thinner and passive

Question 2

The active phase of the 1st stage of labor starts when the cervix is dilated how far?

Answer 2

4 cm

Question 3

What are the normal limits of the latent phase for nulliparous and multiparous women (hours)?

Answer 3

• Nulliparous = up to 20 hours
• Multiparous = up to 14 hours

Question 4

In general how are abnormalities of the latent phase managed?

Answer 4

Therapeutic rest (sleep) + Morphine

Question 5

What are the normal limits of the active phase for cervical dilation (cm/hr) in nulliparous vs. multiparous woman?

Answer 5

• Nulliparous = 1.2 cm/hr
• Multiparous = 1.5 cm/hr

Question 6

Cervical dilation or fetal descent of less than the norm during the active phase constittutes what type of disorder?

Answer 6

Protraction

Question 7

What are the normal limits of the active phase for fetal descent (cm/hr) in nulliparous vs. multiparous woman?

Answer 7

• Nulliparous = 1 cm/hr
• Multiparous = 2 cm/hr

Question 8

How long must no change in cervical dilation and/or fetal descent occur for it to be considered arrest?

Answer 8

• 2 hours or more w/ no cervical dilation
• 1 hour w/ no change in descent/station

Question 9

Dystocia or “difficult labor” results from abnormalities of the thre P’s, which are?

Answer 9

• Power = uterine contractions or maternal expulsive forces
• Passenger = position, size, or presentation of the fetus
• Passage = maternal pelvic bone contractures

Question 11

The diagnosis of dystocia should not be made before what?

Answer 11

An adequate trial of labor has been tried

Question 12

At which contraction rate and/or intensity should you consider augmentation of labor?

Answer 12

Contractions <3 in 10 minutes and/or intensity <25 mmHg

Question 13

ACOG recommends oxytocin in protraction and arrest disordrs after assessing what 4 things?

Answer 13

• Maternal pelvis
• Fetal position
• Station
• Maternal and fetal staus

Question 14

Placing an IUPC to assess “power” requires rupture of membranes, what 2 situations would you NOT want to do this?

Answer 14

• If the station is really high
• Babies head is ballotable (floating upward) upon palpation

Question 15

Minimal effective uterine activity is defined by how many contractions in 10 minutes with an average intensity of how much?

Answer 15

3 contractions in a 10-minute period averaging 25 mmHg above baseline

Question 16

Before proceeding to a C-section should document adequate contractions for at least how long?

Answer 16

At least 4 hours

Question 17

Nulliparous women who present in labor with an unegaged fetal head indicates an increased likelihood of what?

Answer 17

Cephalopelvic disproportion (CPD)

Question 18

Which diameter of the fetal head becomes the presenting diameter during transverse arrest of descent?

Answer 18

Occipitofrontal diameter

Question 19

What is appropriate management of persistent occipitotransverse position if pelvis is adequate, infant is not macrosomic and contractions are inadequate?

Answer 19

• Start oxytocin
• Rotation: manually or Keilland forceps

Question 20

The course of labor if fetal head is in OP position is usually normal, but may see what 2 abnormalities?

Answer 20

• The 2nd stage may be prolonged
• Assoc. w/ considerably MORE back discomfort***

Question 21

What is appropriate management of persistent OP fetal head position?

Answer 21

• Observation if labor continues to be progressive and FHR is normal
• Can use vacuum or forceps (operational delivery)

Question 22

Most common cause of fetal ascites leading to dystocia is what?

Answer 22

Immune hydrops - Rh isoimmunization

Question 23

What are primary risks to mother associated with macrosomia?

Answer 23

• Primary risk = ↑ risk for C-section
• Postpartum hemorrhage and significant vaginal lacerations

Question 24

What are the fetal risks associated with macrosomia during delivery?

Answer 24

• Shoulder dystocia
• Fracture of clavicle
• Damage to nerves of brachial plexus: especially C5-C6 (Erb’s palsy)

Question 25

Most common brachial plexus injury during birth is what?

Answer 25

• Erb-Duschenne
• Upper arm palsy (C5-C6)

Question 26

Due to risk of morbidity for infants and mothers with macrosomia, ACOG recommends prophylactic C-section at what weights for non-diabetic and diabetic patients?

Answer 26

• >5000 grams in NON-diabetic
• >4500 grams in diabetic (these babies often have ↑ AP diameter of their chest!)

Question 27

Which brachial plexus injury is more common with shoulder dystocia?

Answer 27

Klumpke’s palsy (C8 and T1); but Erb’s is still most common

Question 28

If you suspect shoulder dystocia what should you do immediately?

Answer 28

• Obstetric emergency! CALL FOR HELP (anesthesiologist and NICU)
• Initial maneuvers are McRoberts and Suprapubic pressure

Question 29

What is first line and last resort managment of Shoulder Dystocia; what can be done after?

Answer 29

• McRobert’s Maneuver —> Hyerflexion and ABduction of maternal hips
• Suprapubic pressure
• Zavanelli maneuver is last resort –> will need C-section delivery