Maternal Adaptations to Pregnancy I

Question 1

What is chorionic gonadotropin?

Answer 1

Produced by the syncytiotrophoblast shortly after transplantation

Principal actions is to prevent luteolysis and promote progesterone production

Exerts its actions via the LH receptor

Question 2

What is the source and general action of progesterone?

Answer 2

Produced by placenta and corpus luteum

Acts by regulating gene expression in target tissue

90% of porgesterone produced by the placenta is released into maternal circulation

Question 3

What is the principal target and actions of progesterone?

Answer 3

Female reproductive tract

Promotes endometrial differentiation and enhances its secretory function

Prepares endometrium for implantation and faciliatates decidua formation

Acts on cervix to induce mucus productions

Inhibits uterine contractions

Question 4

What is the principal source of estrogen by the 8th week of pregnancy?

Answer 4

Placenta

Collaborative enterprise involving the placenta and fetus

Question 5

What is the major circulating estrogen during pregnancy?

Answer 5

Estriol

Question 6

How does the fetoplacental unit produce estrogens?

Answer 6

Fetal zone of adrenal cortex produces DHEAS

Fetal liver converts DHEAS to 16a-OH-SHEA-S

Placenta converts this to estriol

Question 7

What is chorionic somatomammotropin (hCS)?

Answer 7

Secreted into both maternal and fetal circulation

Stimulates lipolysis and antagonizes the action of insulin, causing glucose levels to rise in the mother

Question 8

What is the placental variant of human growth hormone (hGH-V)?

Answer 8

Secreted by syncytiotrophoblast

Has GH-like actions and causes circulating IGF-1 to rise

Causes decline in pituitary GH levels in maternal blooc (negative feedback)

Question 9

What occurs to uterine smooth muscle in pregnancy?

Answer 9

Increase due to myocyte hypertrophy

Increase in fibrous and elastic tissue content

Question 10

Describe the changes in uterine blood flow during pregnancy

Answer 10

Uterine arterioles are maximally dilated throughout pregnancy

Low resistance uteroplacental ciruclation acts like an arteriovenous shunt causing:

• decrease in peripheral resistance
• increase in cardiac output

Question 11

What changes occur to the cardiac output and systemic vascular resistance in the maternal circulation during pregnancy?

Answer 11

Cardiac output increases

Systemic vascular resistance falls

Question 12

What factors cause the fall in SVR during pregnancy?

Answer 12

Low resistance uteroplacental circulation

Humoral factors:

Estrogen - stimulates production of prostacyclins and NO

Progesterone

Relaxin

Question 13

What causes the increase in cardiac output during pregnancy?

Answer 13

Increase in stroke volume and heart rate

Increased diastolic volume (preload) and reduced afterload (lower resistance)

Question 14

What is supine hypotensive syndrome?

Answer 14

When the mother shifts from laying to a supine position, the weight of the uterus compresses the IVC, decreasing venous return and arterial pressure

Question 15

What are the changes in blood volume during pregnancy?

Answer 15

Blood volume increases about 40-50%

Increase in plasma volume is greater than the increase in RBCs, leading to a decreased hematocrit

Question 16

Describe the changes in blood pressure during pregnancy

Answer 16

Systolic, diastolic, and MAP pressures decline throughout pregnancy due to a disproportionate decrease in peripheral vascular resistance

Pulse pressure widens because DBP falls more than SBP

Question 17

What changes are associated with albumin during pregnancy?

Answer 17

Concentration decreases, causing a decrease in oncotic pressure

Liver sensitivity to lowered oncotic pressure is reduced, so it doesn’t produce more to compensate

Decrease in hematocrit and plasma albumin content lowers blood viscosity

Question 18

What occurs to circulating levels of fibrinogen, clotting factors, and binding globulins in pregnancy?

Answer 18

Increase

Estrogen stimulates synthesis of binding globulins

Elevated levels of fibrinogen and other clotting factors may serve to prevent postpartum hemorrhage

Question 19

What is the result of the increase in renal vasodilation during pregnancy?

Answer 19

Increase in renal blood flow

Increase in GFR

Question 20

What changes are associated with the increased GFR during pregnancy?

Answer 20

Decreased serum creatinine, urea and uric acid

Increase in urinary protein excretion

Increase in size of the glucose load being filtered – can lead to glycosuria

Question 21

What changes are associated with sodium balance during pregnancy?

Answer 21

Sodium retention occurs

This is causes the increased plasma volume associated with pregnancy

Question 22

What occurs to the RAA system during pregnancy?

Answer 22

Renin, angiotensinogen and aldosterone levels all increase during pregnancy

Uterus secretes renin during pregnancy

Estrogen and progesterone stimulate renin activity

Estrogen stimulates hepatic angiotensinogen synthesis