2. physiological changes in pregnancy

Question 1

Post-fertilisation, what enzyme does the blastocyst produce and what structure produces it?
What is the function of this enzyme?
Give a clinical use of this enzyme.
Which symptom of pregnancy does this enzyme cause?

Answer 1

• β-hCG (beta- human chorionic gonadotropin), it is produced by the trophoblast of the blastocyst.
• B-hCG continues to support the corpus luteum after fertilisation so it will continue to produce progesterone. - The continued production of progesterone ensures that the uterus lining is getting sustained for the blastocyst to attach itself to.
• This enzyme can be used for pregnancy testing as it is detectable 10 days after fertilisation.
• Morning sickness.

Question 2

When does the placenta take over oestrogen and beta-hCG production?

Answer 2

10-12 weeks.

Question 3

Low levels of ______ hormone suggest an ectopic pregnancy.

Answer 3

beta-hCG.

Question 4

Explain the role of progesterone in miscarraiges.

Answer 4

No progesterone = endometrium cant develop and so will eventually shed along with the developing embryp.

Question 5

Which 4 hormones are produced by the placenta?

Answer 5

Progesterone.
Oestrogen.
beta-hCG.
Human placental lactogen.

Question 6

Which three areas of the body/physiology does progesterone affect?

Answer 6

Uterus, breast and homeostasis.

Question 7

Why might women suffering from asthma find their asthmatic symptoms are improved during pregnancy?

Answer 7

Progesterone will act as a smooth muscle relaxant and so will relax (dilate) the smooth muscles of the bronchi.

Question 8

Give two examples of how progesterone plays a role in homeostasis during pregnancy.
“Think of breathing and urine”.

Answer 8

• increased respiratory centre hypersensitivity due to increased sensitivity of the respiratory receptors to CO2.
• increased sodium reabsorption through increased activity of renin system.

Question 9

Give two examples of how progesterone affects breast tissue during pregnancy.

Answer 9

• increases lobule development.

- inhibits milk production.

Question 10

Give 4 examples of how oestrogen affects the uterus during pregnancy.

Answer 10

• allows myometrium to grow.
• connexin insertion.
• oxytocin receptor insertion into myometrium which prepares uterus for the contractile element required for labour.
• Prostaglandin production which is important for the softening of the cervix.

Question 11

How does oestrogen affect the breast tissue?

Answer 11

• contributes to breast duct development but it inhibits milk production.

Question 12

Which intermediate, required for the synthesis of oestrogen, is not present in the placenta?

Answer 12

DHEA.

Question 13

How does the placenta synthesis oestrogen?

Answer 13

• the placenta will release CRH.
• CRH will act on the baby’s anterior pituitary, triggering it to produce adrenocorticotropic hormone (ACTH).
• ACTH will act on the adrenal cortex and trigger it to produce cortisol.
• this cortisol can be used to make DHEA.
• the DHEA is transported to the mother’s placenta, where it can be used to synthesis oestrogen.

Question 14

Which hormone in pregnancy is responsible for uterus smooth muscle relaxation (to prevent fetal expulsion) and the formation of a cervical plug?

Answer 14

Progesterone.

Question 15

What is the probable pathway via which lung maturation occurs in the foetus?

Answer 15

• placenta will release CRH, which will also act on mother’s anterior pituitary.
• anterior pituitary will release ACTH.
• ACTH will act on mother’s adrenal cortex to produce cortisol.
• this cortisol is likely involved in the foetuses lung maturation.

Question 16

Give three examples of how human placental lactogen affects the mother.

Answer 16

• increased lipid breakdown and the release of free fatty acids.
• breast development.
• insulin resistance resulting in decreased glucose utilisation therefore increased levels of blood glucose.

Question 17

Give two examples of how human placental lactogen affects the foetus.

Answer 17

• the increased blood glucose from the mother can be used to promote growth in the foetus.

Question 18

What causes the symptoms of FUNCTIONAL anaemia in pregnant women?

Answer 18

• although the blood volume increases due to increase in plasma levels, the RBC levels don’t increase enough with it.
• therefore, this is due to hemodilation.

Question 19

The lack of which two substances causes pathological anaemia in pregnant women?

Answer 19

• iron and folic acid.

Question 20

Describe the physiological changes of “clotting” that take place in pregnancy.

Answer 20

• there is a decrease in anti-thrombotic factors resulting in a higher proportion of pro-thrombotic factors.

Question 21

How does the foetus affect the mother’s heart?

Answer 21

Due to the growing abdominal mass, the heart can get displaced and will move outwards and upwards.

Question 22

What is the equation for blood pressure?

Answer 22

BP = CO x SVR.

Question 23

What is the equation for cardiac output?

Answer 23

CO = SV x HR.

sv - stroke volume.

Question 24

What is the stroke volume?

Answer 24

The amount of blood pumped out after each heartbeat.

Question 25

How does stroke volume vary between a pregnant and non-pregnant woman? Why?

Answer 25

Stroke volume increases during pregnancy. Oestrogen is responsible for this bc it increases the contractility of the heart muscles.

Question 26

What is the cardiac output?

Answer 26

Volume of blood pumped by the heart each minute.

Question 27

How does blood pressure change during pregnancy? And when does this change occur?

Answer 27

Typically in the second trimester there is a decrease in mean blood pressure usually mediated by a decrease in diastolic BP. Systolic BP changes very little.

Question 28

Why does varicose veins occur in pregnant women?

Answer 28

Pressure of the uterus sitting on the inferior vena cava.

Question 29

Why is the mother advised to lie on their left side?

Answer 29

Bc lying supine can cause the uterus to put pressure on the inferior vena cava.

Question 30

Why does the mother tend to feel breathless during pregnancy?

Answer 30

The increased progesterone increases sensitivity to carbon dioxide through increase in central chemoreceptors. As a result ventilation increases causing the mother hyperventilate.

Question 31

What is the main cause of increased urine frequency in pregnancy?

Answer 31

The uterus puts pressure on the bladder.

Question 32

Why is glucose detected in the urine of pregnant women?

Answer 32

Due to an increase in plasma volume in pregnancy, the GFR increases in the glomerulus. Bc there is a higher volume of fluid passing through the tubules, the amount of glucose exceeds the reabsorption rate and so resulting in some excess glucose in the urine.

Question 33

What causes swollen ankles in pregnant women?

Answer 33

Due to increased retention of sodium and water. Some of the fluid leaks into the interstitium as observed in swollen ankles.

Question 34

Name 4 changes in the breast that occur during pregnancy.

Answer 34

Darkening of the areola.
Increased glandular tissue.
Increased vascularity.
Hyperplasia of fat deposits.

Question 35

How do progesterone and oestrogen interact with prolactin?

Answer 35

They inhibit prolactin so milk production doesn’t occur.

Question 36

What role does the placenta play in milk production post-pregnancy?

Answer 36

As the placenta is removed, so is the production of oestrogen and progesterone. Therefore prolactin isn’t inhibited anymore and milk production can occur.

Question 37

Why is there no chance of ovulation during the initial weeks after pregnancy?

Answer 37

Bc prolactin is being produced for lactation. Prolactin inhibits GnRH and so FSH and LH aren’t produced.

Question 38

What hormones does the posterior pituitary gland produce?

Answer 38

Oxytocin and ADH.

Question 39

How is oxytocin relevant during labour and post-delivery?

Answer 39

Causes uterine contraction. Causes milk ejection via myoepithelial cell contraction.