Physio of Preg., Labor, and Delivery Flashcards
What are some mechanical changes that happen in mom’s thorax while pregnant?
Expanded circumference.
Subcostal angle becomes less acute.
Diaphragm rises higher.
Why might pregnant women get non-infectious or allergic nasal stuffiness and epistaxis?
Estrogen induces hyperemia and edema in the upper respiratory tract.
How does lung volume change in pregnancy? Implication?
Greater tidal volume, greater minute ventilation, less reserve.
Less reserve means more likely to have severe complications of asthma and resp. infections.
Is dyspnea of pregnancy common? What do you want to rule out?
Yes - happens to 60-70% of patients in later first or early second trimester.
Definitely rule out PE.
How does cardiac output change in pregnancy? What percentage does the uterus get?
Increases from about 4.5L/min to 6L/min.
Uterus will get about 17% of cardiac output by term.
How can physical posture affect C.O.?
Late in pregnancy, lying on back can cause gravid uterus to compress the IVC, decreasing C.O. and making everyone uncomfortable.
How do pregnant women adjust to the greater blood volume they have?
Progesterone decreases peripheral vascular resistance -> lower BP.
What is an observable effect of these CV changes on the heart?
Systolic ejection murmur is common.
diastolic murmur is not normal
Effect of increased body water on electrolytes?
Slightly reduced Na+ concentration, but not hyponatremic.
Do plasma volume and RBC volume increase by the same amount? What effect does this have? Why might this be good?
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.
What specific effects does estrogen have on coagulation?
Increases Factors I, VII, VIII, IX, and X.
Do PT and aPTT remain valid tests during pregnancy?
Yes.
How might you detect bleeding that you can’t see in a pregnant woman?
Bleeding will cause a drop in fibrinogen
Renal changes of pregnancy?
Renal hypertrophy, higher risk for infections, especially on the right side.
The uterus tends to rotate toward the right side…
Effect of pregnancy hormones on the kidney?
Progesterone causes dilated ureters and renal pelvises.. increased GFR… drop in creatinine… renal stuff.
Impact of progesterone on the GI tract?
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)
3 liver products increased in pregnancy?
Should LFTs be normal?
Fibrinogen, binding proteins (for steroids / thyroid hormone), clotting factors.
LFTs should be normal.
When does most nausea/vomiting of pregnancy occur?
4-16 weeks.
What are the 3 P’s of getting a baby out?
Passenger
Passage
Powers (“Push it.”)
3 aspects of the “passenger” that affect delivery?
Presentation (cephalic vs. breach / transverse)
Size
Position (which way head is facing)
Which position of the head is ideal as the baby is coming out?
Occiput-Anterior (face-down)
What is the “zero station”?
The ischial spines.
If the cervix is dilated by the baby isn’t descended, what do you suspect?
Cephalopelvic dysproportion.
4 things that induce uterine contraction, physiologically?
Prostaglandins (E2, F2alpha)
Anything that increases intracelullar Ca++
Gap junctions
Increased oxytocin receptors
2 things that help cervical ripening?
Collagenase, elastase.
Difference in cervical effacement and dilation in first vs. repeat pregnancy?
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).
What effect does cortisol have on uterine contraction?
Progesterone inhibits contraction. Estrogen promotes contraction (through upregulated oxytocin receptors).
Cortisol promotes conversion of progesterone to estrogen.
Do progesterone levels drop during labor?
Surprisingly, no. They may be outcompeted by glucocorticoids…
Review: What is normal cutoff for “term” labor?
After 37 weeks. Mean is at 40 weeks from LMP.
3 stages of labor?
Stage 1: closed, fully dilated
Stage 2: fully dilated - delivery
Stage 3: placenta
What are the 2 phases of stage 1 of labor?
Latent: variable duration, slow cervical dilation
Active: faster rate of cervical change, regular uterine contractions.
What do modern data (the Zhang curve) say is the usual amount of cervical dilation at which the shift to rapid dilation occurs?
at about 4-6cm.
3 signs of placental separation post-delivery of the baby? When should this occur?
Increased bleeding
Lengthening of the cord
Uterus rises, changes shape (discoid -> globular… whatever that means).
Should occur within 30 minutes of delivery.
CV changes during / after labor?
Increase in C.O. by 10-15%, because blood no longer going to uterus.
Women must be kept on telemetry due to arrhythmia risk.
4 degrees of birthing lacerations?
1st: vaginal mucosa, perineal skin
2nd: subcutaneous tissue
3rd: anal sphincter
4th: rectal mucosa
4 operative delivery options?
Forceps
Vacuum
C-section
C-hysterectomy
Main indication for C-hysterectomy?
Placental acreta - placenta too deeply imbedded in uterus, won’t come out, and mom will bleed out if not removed.
What is dystocia? What injury is often caused?
Ant. shoulder gets stuck on pubic symphysis.
Pulling -> brachial plexus injury (don’t ask me which one…)
What is monitored with External Fetal Monitoring? What’s a really worrisome sign (there are probably many..)?
Heart rate, uterine contractions.
Worrisome when fetal heart rate dips after contractions.
1 downside mentioned about C-sections in terms of later pregnacy?
May increase risk of placental acreta in later pregnancy.
