Physiology of Pregnancy

Question 1

Human Placental Lactogen (hPL)
• Composition
• How do levels change throughout pregnancy?
• Function?

Answer 1

Composition:
• hPL is a PEPTIDE hormone without any carbohydrate component

Change in levels:
• Levels increase steadily throughout pregnancy

Function:
• hPL increases blood glucose (increased Gluconeogenesis, decreased glucose uptake)
• hPL increases lipolysis

Question 2

Human Placental Lactogen (hPL)
•Is it needed to maintain pregnancy?
• Why might this cause Ketones in the urine?
• Consequences of XS hPL on the fetus?

Answer 2

NOT Needed to maintain pregnancy

• Ketone are typically seen in the urine of women in L and D because of increased lipolysis (anti-insulin action) of hPL
• Exposure of the fetus to hyperglycemic condition can lead to hyperinsulinemia (causing post-partum hypoglycemia) and macrosomia (from xs nutrients and insulin (anabolic))

Question 3

What cells are responsible for the release of hCG?

Answer 3

Syncytiotrophoblasts

Question 4

What are the 3 (maybe 4) primary functions of hCG?

Answer 4

1. Prolongs the life of the corpus luteum
2. Increases steroid production
3. Diagnostic test for pregnancy
4. May help depress mom’s immune system

Question 5

What are the 2 main mediators secreted from the placenta?

• what are their functions?

Answer 5

1. Estrogen - stimulates the endometrium and controls uterine blood flow
2. Progesterone - affects tubal mobility, endometrial maturation, blood flow, relaxes muscle, INHIBITS LYMPHOCYTE MEDIATED rejection

Question 6

When do hCG levels max out during pregnancy?

• how high to they get?

Answer 6

Max out at ~ 8 wks

They get up to around 100,000. Much higher than this and you should consider hydatidiform mole or choriocarcinoma

Question 7

What is Hegar’s sign?
• when does it occur?
• what causes it?

Answer 7

Lower Uterine Segment Softening
• occurs around wk 6

Cause:
• Increased Volume in veins without a significant increase in plasma proteins (decreased intrvascular oncotic pressure) as well has increased hydrostatic pressure from the fetus pressing on the intraabdominal veins

Question 8

What is Chadwick’s sign?
• when does it occur?
• what causes it?

Answer 8

Bluish Discoloration
• occurs wk 6-8

Cause:
Increased Vascularity

Question 9

What is Goodell’s sign?

• when does it occur?

Answer 9

Cervical Softening

• Occurs at week 8

Question 10

What histological changes do we see in the cervix during pregnancy?

Answer 10

Replacement of squamous epithelium with columnar epithelium

Question 11

At how many weeks should the uterus be roughly the size of a baseball?
• Softball?

Answer 11

8 wks - baseball

10 wks - softball

Question 12

At how many weeks of pregnancy does the uterus go from being a pelvic organ to an intraabdominal organ?
• when does it get to the umbilicus?

Answer 12

12 wks - crosses pelvic brim

20 wks - Fetus should be to umbilicus

Question 13

When will be fetus be just below the xiphoid?

Answer 13

36 wks

Question 14

During what week of pregnancy are aldosterone levels at their highest?

Answer 14

34 wks

Question 15

What happens to PTH levels in pregnancy?

• Total and free ionized Calcium levels?

Answer 15

PTH increases

Total calcium decreases but FREE CALCIUM IS THE SAME

Question 16

T or F: in addition to multiple hydatidiform moles, choriocarcinomas, and erythroblastosis, multiple gestations can also cause increases in hCG.

Answer 16

True, more fetus => more placenta => more hCG

Question 17

What happens to maternal thyroid function in pregnancy?

Answer 17

TSH levels may decrease early in pregnancy due to suppression by hCG

TSH levels them rise to normal with an ENLARGED thyroid that is needed because there is more TBG

BMR increases but free T3 and T4 are NORMAL

(free T4 actually falls late in pregnancy, don’t know why)

Question 18

What is the normal amount of weight gained during pregnancy?

Answer 18

24 lbs (1st - 2, 2nd - 11, 3rd - 11)

Question 19

What factors increase a pregnant woman’s susceptibility to UTIs?

Answer 19

1. Increased Renal BF => Increased GFR => increased glycosuria
2. Ureters dilated from increased pressure at the pelvic brim => decreased tone and peristalisis

combine these two and you get stasis + glucose in urine => way more likely to get UTI

Question 20

What volumes and capacities decrease in pregnancy?
• which increase?
• Which do not change?

Answer 20

Decrease:
Reduced RV => Reduced TLV => Reduced FRC (expiratory reserve vol.)

Increased:
Tidal Volume

Unchanged:
IRV - inspiratory reserve volume, Vital Capacity

Basically you just exhale more with each breath and you have less RV

Question 21

What is the compensation in pregnancy that leads to increased TV and respiratory alkalosis?

Answer 21

1. Widening of subcostal angle
2. Increased Diphragmatic Excursion (pushes more air out)
3. Tidal volume increased
4. Minute ventilation increased
5. pO2 increasd pCO2 decreased
6. Respiratory alkalosis

Question 22

What do you get a widely split S1 with S3 + soft mid-systolic flow murmur in pregnancy?

Answer 22

More anemia during pregnancy (caused by increase in blood volume that is not compensated completely by increase in RBCs)

Question 23

What changes do we wee in cardiac output with pregnancy?

Answer 23

Increased SV + NL or inc HR => higher CO (peaks at 30-32 wks)

Increased SV with Decreased TPR => lower BP

Question 24

Explain what causes increased RBCs in pregnancy?

Answer 24

increase hPL => increaed EPO => increased erythroid hyperplasia => increased reticulocytes

Although this compensation is effective, its not good enough to overcome the 45% increase in plasma volume in pregnancy