OB physiology

Question 1

What causes relative hemodilution of pregnancy?

Answer 1

There is a 36% increase in maternal blood volume, with a 47% increase in plasma and only a 17% increase in RBC mass. MCV is normal.

Question 2

What is peripartum cardiomyopathy?

Answer 2

An idiopathic cardiomyopathy that presents with heart failure secondary to left ventricular systolic dysfunction towards the end of pregnancy or the several months following delivery. Symptoms include fatigue, SOB, palpitations, and edema.

Question 3

How does the minute ventilation change in pregnancy?

Answer 3

Increases which causes a compensatory respiratory alkalosis

Question 4

What are the PFT changes seen in pregnancy?

Answer 4

Increased inspiratory capacity, tidal volume, and minute ventilation (minute ventilation is increased because of increase in TV, respiratory rate remains normal). Decreased functional reserve capacity, expiratory reserve capacity, and residual volume

Question 5

How does systemic vascular resistance change in pregnancy?

Answer 5

Decreases

Question 6

What are common causes of acute pulmonary edema in pregnancy?

Answer 6

The plasma osmolarity during pregnancy decreases which increases susceptibility to pulmonary edema. Common causes of acute pulmonary edema include tocolytic use, cardiac disease, fluid overload, and preeclampsia

Question 7

What type of heart murmur is very common to hear in pregnant women?

Answer 7

Up to 95% of women will have a systolic murmur due to increased blood volume. Diastolic murmurs are always abnormal.

Question 8

How much does cardiac output increase by during pregnancy?

Answer 8

33%

Question 9

How do thyroid labs change during pregnancy?

Answer 9

There is an increase in thyroid binding globulin (TBG) due to increased circulating estrogen. This causes a rise in total T3 and T4, however, free T3 and T4 remain normal. TSH remains normal.

Question 10

What are the weight gain guidelines for pregnancy?

Answer 10

Underweight (BMI <18.5): 28-40 lbs
Normal weight (BMI 18.5-24.9): 25-35 lbs
Overweight (BMI 25-29.9): 15-25 lbs
Obese (BMI >30): 11-20 lbs

Question 11

What are the renal and urinary changes that are seen in a normal pregnancy?

Answer 11

Increased renal blood flow, glomerular filtration rate, renal basement membrane permeability, and renal protein excretion. Decreased BUN and serum creatinine.

Question 12

What is the physiology behind the development of pulmonary edema in preeclampsia?

Answer 12

Generalized arterial vasospasm increases afterload on the heart, which increases pulmonary capillary pressure. This is exacerbated by low albumin, decreased renal function, and increased vascular permeability

Question 13

What are the lab value changes seen in hyperemesis gravidarum?

Answer 13

Hypochloremic metabolic alkalosis, hypokalemia, hypoglycemia, and elevated serum aminotransferases - due to protracted vomiting

Question 14

How does mean arterial pressure change in pregnancy?

Answer 14

Decreases (due decreased systemic vascular resistance, which is more than the increased cardiac output seen)

Question 15

What contributes to the increased coagulability seen in pregnancy?

Answer 15

Increased vWF, increased factors 7, 8, 10, increased tPA inhibitor, decreased factors C and S, increased fibrinogen

Question 16

How does serum creatinine change in pregnancy?

Answer 16

Decreases (normal in pregnancy is 0.4-0.8). This is due to increased GFR

Question 17

What acid-base changes are seen in pregnancy?

Answer 17

Respiratory alkalosis due to increased minute ventilation. This causes a slight decrease in serum bicarb (example: pH 7.45, PO2 103, PCO2 28, HCO3 18)

Question 18

How does the leukocyte count change in pregnancy?

Answer 18

Slightly increased

Question 19

How does the ureteral caliper change in pregnancy?

Answer 19

Dilated

Question 20

What GI changes are seen in pregnancy?

Answer 20

Delayed stomach emptying, decreased lower esophageal sphincter tone, and decreased gut motility

Question 21

Is a PCO2 of 40 normal in pregnancy (normal for non-pregnant adults is 35-45)?

Answer 21

It indicates significant CO2 retention and possible impending respiratory failure

Question 22

What is considered anemia in pregnancy?

Answer 22

Hgb <10.5 g/dL

Question 23

How much does plasma volume increase by in pregnancy?

Answer 23

By 50%

Question 24

Is glucose in the urine of a pregnant woman normal?

Answer 24

Yes - the increased GFR causes glucose to be lost in urine commonly