Physio of Preg., Labor, and Delivery

Question 1

What are some mechanical changes that happen in mom’s thorax while pregnant?

Answer 1

Expanded circumference.
Subcostal angle becomes less acute.
Diaphragm rises higher.

Question 2

Why might pregnant women get non-infectious or allergic nasal stuffiness and epistaxis?

Answer 2

Estrogen induces hyperemia and edema in the upper respiratory tract.

Question 3

How does lung volume change in pregnancy? Implication?

Answer 3

Greater tidal volume, greater minute ventilation, less reserve.
Less reserve means more likely to have severe complications of asthma and resp. infections.

Question 4

Is dyspnea of pregnancy common? What do you want to rule out?

Answer 4

Yes - happens to 60-70% of patients in later first or early second trimester.
Definitely rule out PE.

Question 5

How does cardiac output change in pregnancy? What percentage does the uterus get?

Answer 5

Increases from about 4.5L/min to 6L/min.

Uterus will get about 17% of cardiac output by term.

Question 6

How can physical posture affect C.O.?

Answer 6

Late in pregnancy, lying on back can cause gravid uterus to compress the IVC, decreasing C.O. and making everyone uncomfortable.

Question 7

How do pregnant women adjust to the greater blood volume they have?

Answer 7

Progesterone decreases peripheral vascular resistance -> lower BP.

Question 8

What is an observable effect of these CV changes on the heart?

Answer 8

Systolic ejection murmur is common.

diastolic murmur is not normal

Question 9

Effect of increased body water on electrolytes?

Answer 9

Slightly reduced Na+ concentration, but not hyponatremic.

Question 10

Do plasma volume and RBC volume increase by the same amount? What effect does this have? Why might this be good?

Answer 10

Plasma volume increases more, causing “physiologic anemia of pregnancy” -> decreased hematocrit.
This may actually be protective against hemorrhage, and help exchange of nutrients/waste/temperature.

Question 11

What specific effects does estrogen have on coagulation?

Answer 11

Increases Factors I, VII, VIII, IX, and X.

Question 12

Do PT and aPTT remain valid tests during pregnancy?

Answer 12

Yes.

Question 13

How might you detect bleeding that you can’t see in a pregnant woman?

Answer 13

Bleeding will cause a drop in fibrinogen

Question 14

Renal changes of pregnancy?

Answer 14

Renal hypertrophy, higher risk for infections, especially on the right side.
The uterus tends to rotate toward the right side…

Question 15

Effect of pregnancy hormones on the kidney?

Answer 15

Progesterone causes dilated ureters and renal pelvises.. increased GFR… drop in creatinine… renal stuff.

Question 16

Impact of progesterone on the GI tract?

Answer 16

All smooth muscle contractions are impaired, predisposing to…
Delayed stomach emptying.
Acid reflux.
Constipation.
Slow gall bladder emptying -> stones.
(increased portal venous pressure -> hemorrhoids… not sure if this is due to smooth muscle)

Question 17

3 liver products increased in pregnancy?

Should LFTs be normal?

Answer 17

Fibrinogen, binding proteins (for steroids / thyroid hormone), clotting factors.
LFTs should be normal.

Question 18

When does most nausea/vomiting of pregnancy occur?

Answer 18

4-16 weeks.

Question 19

What are the 3 P’s of getting a baby out?

Answer 19

Passenger
Passage
Powers (“Push it.”)

Question 20

3 aspects of the “passenger” that affect delivery?

Answer 20

Presentation (cephalic vs. breach / transverse)
Size
Position (which way head is facing)

Question 21

Which position of the head is ideal as the baby is coming out?

Answer 21

Occiput-Anterior (face-down)

Question 22

What is the “zero station”?

Answer 22

The ischial spines.

Question 23

If the cervix is dilated by the baby isn’t descended, what do you suspect?

Answer 23

Cephalopelvic dysproportion.

Question 24

4 things that induce uterine contraction, physiologically?

Answer 24

Prostaglandins (E2, F2alpha)
Anything that increases intracelullar Ca++
Gap junctions
Increased oxytocin receptors

Question 25

2 things that help cervical ripening?

Answer 25

Collagenase, elastase.

Question 26

Difference in cervical effacement and dilation in first vs. repeat pregnancy?

Answer 26

In first labor, cervix gets to efface completely for dilating.
In subsequent labors, will often dilate without much effacement (can surprise you by rapidly progressing).

Question 27

What effect does cortisol have on uterine contraction?

Answer 27

Progesterone inhibits contraction. Estrogen promotes contraction (through upregulated oxytocin receptors).
Cortisol promotes conversion of progesterone to estrogen.

Question 28

Do progesterone levels drop during labor?

Answer 28

Surprisingly, no. They may be outcompeted by glucocorticoids…

Question 29

Review: What is normal cutoff for “term” labor?

Answer 29

After 37 weeks. Mean is at 40 weeks from LMP.

Question 30

3 stages of labor?

Answer 30

Stage 1: closed, fully dilated
Stage 2: fully dilated - delivery
Stage 3: placenta

Question 31

What are the 2 phases of stage 1 of labor?

Answer 31

Latent: variable duration, slow cervical dilation
Active: faster rate of cervical change, regular uterine contractions.

Question 32

What do modern data (the Zhang curve) say is the usual amount of cervical dilation at which the shift to rapid dilation occurs?

Answer 32

at about 4-6cm.

Question 33

3 signs of placental separation post-delivery of the baby? When should this occur?

Answer 33

Increased bleeding
Lengthening of the cord
Uterus rises, changes shape (discoid -> globular… whatever that means).
Should occur within 30 minutes of delivery.

Question 34

CV changes during / after labor?

Answer 34

Increase in C.O. by 10-15%, because blood no longer going to uterus.
Women must be kept on telemetry due to arrhythmia risk.

Question 35

4 degrees of birthing lacerations?

Answer 35

1st: vaginal mucosa, perineal skin
2nd: subcutaneous tissue
3rd: anal sphincter
4th: rectal mucosa

Question 36

4 operative delivery options?

Answer 36

Forceps
Vacuum
C-section
C-hysterectomy

Question 37

Main indication for C-hysterectomy?

Answer 37

Placental acreta - placenta too deeply imbedded in uterus, won’t come out, and mom will bleed out if not removed.

Question 38

What is dystocia? What injury is often caused?

Answer 38

Ant. shoulder gets stuck on pubic symphysis.

Pulling -> brachial plexus injury (don’t ask me which one…)

Question 39

What is monitored with External Fetal Monitoring? What’s a really worrisome sign (there are probably many..)?

Answer 39

Heart rate, uterine contractions.

Worrisome when fetal heart rate dips after contractions.

Question 40

1 downside mentioned about C-sections in terms of later pregnacy?

Answer 40

May increase risk of placental acreta in later pregnancy.