The Uterus and Labor

Question 1

What is uterine blood flow (mL/min) in the non-pregnant patient?

Answer 1

100 mL/min

Question 2

How is uterine blood flow regulated?

Answer 2

It is not autoregulated

Dependent on MAP, cardiac output, and uterine vascular resistance

Question 3

What is the formula for uterine blood flow?

Answer 3

uterine BF= (U artery pressure - U venous pressure ) / U vascular resistance

Question 4

What are causes of decreased uterine blood flow?

Answer 4

Decreased perfusion (hypotension, hemorrhage, aortocaval compression)

Increased resistance (uterine contraction, hypertensive conditions)

Question 5

What does the first stage of labor entail?

Answer 5

Beginning of regular contractions to full cervical dilation (10cm)

Question 6

What does the second stage of labor entail?

Answer 6

Full cervical dilation to delivery of the fetus

Pain in perineum begins during stage two

Question 7

What does stage three entail?

Answer 7

Delivery of the placenta

Question 8

What part of the graph represents the latent phase of labor?

Answer 8

A

Question 9

What part of the graph represents the active phase of labor?

Answer 9

B

Question 10

What part of the graph represents the first stage of labor?

Answer 10

The blue and green shaded area

Question 11

What part of the graph represents the second stage of labor?

Answer 11

The pink shaded area

Question 12

What part of the graph represents the thirst stage of labor?

Answer 12

The purple shaded areas

Question 13

What part of the graph represents the thirst stage of labor?

Answer 13

The purple shaded area

Question 14

What are ASA guidelines regarding NPO status in laboring mothers?

Answer 14

Drink moderate amount of clear liquids throughout labor

Eat solid foods up to the point of neuraxial blockade

Question 15

How does placing an epidural affect labor progression?

Answer 15

It does not prolong the first stage of labor

It does not increase the need for a cesarean section

Question 16

To what nerve roots do pain signals travel during the first stage of labor?

Answer 16

T10- L1 posterior nerve roots

Question 17

To what nerve roots do pain signals travel during the second stage of labor?

Answer 17

S2- S4 posterior nerve roots

Question 18

What is the afferent pathway of the first stage of labor?

Answer 18

Visceral C fibers of the hypogastric plexus

Question 19

What regional techniques cover pain felt in the first stage of labor?

Answer 19

Neuraxial (spinal, epidural, CSE)

Paravertebral lumbar sympathetic block

Paracervical block

Question 20

What is the main risk associated with a paracervical block?

Answer 20

High risk of fetal bradycardia

Question 21

What is the afferent pathway of the second stage of labor?

Answer 21

Pudendal nerve

Question 22

What regional techniques address pain associated with the second stage of labor?

Answer 22

Neuraxial (spinal, epidural, CSE)

Pudendal nerve block

Question 23

How does uncontrolled pain affect the mother and fetus physiologically?

Answer 23

Increased maternal catecholamines > hypertension and reduced uterine blood flow

Maternal hyperventilation > leftward shift of oxyHgb curve > reduced delivery of O2 to the fetus

Question 24

How can N2O be used as an analgesia during labor?

Answer 24

50% N2O + 50% O2 self- administered via facemask

Question 25

What are some benefits of N2O as an analgesia for labor?

Answer 25

Not associated with hypoxia, loss of airway reflexes, or unconsciousness

Preserves uterine contractility

Does not cause neonatal depression

Question 26

What is the benefit of a CSE?

Answer 26

Provides rapid onset of spinal anesthesia and the ability to prolong the duration of anesthesia with an indwelling catheter.