Placental Development and Physiology + Multiple Pregnancy

Question 1

What is kind of disease is pre-eclampsia and what causes it?

Answer 1

Multi-organ disease, placenta

Question 2

When is pre-eclampsia cured?

Answer 2

After birth

Question 3

Why does gestational diabetes cause a large baby?

Answer 3

Bc glucose stimulates growth in baby

Question 4

What consequence can gestational diabetes lead to?

Answer 4

Stillbirth

Question 5

What keeps the early embryo alive?

Answer 5

Decidua

Question 6

Describe placental morphogenesis

Answer 6

1) The placenta develops over the entire surface of the chorion and then at 16 weeks regresses to form the discoid placenta
2) Elevated levels of oxidative stress in the peripheral regions of normal pregnancies leads to villous regression and formation of the smooth chorion leavae (hyper oxygenation at the top)

Question 7

Describe the early placenta

Answer 7

Completely envelops the embryo

Question 8

Describe the early embryo

Answer 8

Very anoxic, surviving on only what is produced by granular cells in the early placenta

Question 9

What can a functional MRI pick up on in a placenta?

Answer 9

Oxygen function and cervical softening

Question 10

Describe the trophoblast plug

Answer 10

During early pregnancy the volume of the endovascular trophoblast is such that it plugs the mouths of the spiral arteries, preventing maternal blood flow into the placenta

Question 11

What does the trophoblast plug coincide with?

Answer 11

The period of histiotrophic nutrition (diffusion, anoxic)

Question 12

What is the histiotroph?

Answer 12

Nutritional material in spaces between the maternal and fetal tissues, derived from the maternal endometrium and the uterine glands, not from maternal blood flow

Question 13

How thick is the maternal endometrium at 6 weeks?

Answer 13

5-6mm with highly active glands

Question 14

What is the decidua?

Answer 14

Thick endometrium

Question 15

Name 3 angiogenic factors active in early fetal and placental growth

Answer 15

1) VEGF = vascular endothelial factor
2) hCG = human chorionic gonadotrophin
3) hPL = human placental lactogen

Question 16

Describe the action of progesterone in early fetal and placental growth

Answer 16

1) Progesterone stimulates glands (decidual cells) which produce prolactin
2) Prolactin stimulates glandular epithelium cells to produce the angiogenic factors, stimulating growth and proliferation of the embryo (and placenta?)

Question 17

What are the 4 functions of the placenta?

Answer 17

1) Respiratory organ (controls gas exchange)
2) Nutrient transfer
3) Excretion of fetal waste products (like kidney)
4) Hormone synthesis

Question 18

Describe the structure of the placenta at term

Answer 18

• Lobules in placenta, intercepted by septum
• Frongs contain smaller blood vessels from umbilical arteries and veins, essential for getting nutrients from mother to baby

Question 19

What is the syncytiotrophoblast?

Answer 19

Line of cells between septum and villi with umbilical vessels highly specialised for transport

Question 20

When does maternal and fetal blood come into direct contact?

Answer 20

Only at birth

Question 21

Describe the transfer of blood from mother to fetus

Answer 21

Mother’s blood comes through arteries → syncytiotrophoblast → fetal circulation

Question 22

How does maternal uterine blood flow changes with gestational age?

Answer 22

It increases greatly

Question 23

Describe cells of the syncytiotrophoblast

Answer 23

• Syncytium (connected)
• Large nuclei
• No cell walls
• Brush border like kidney and gut (transport)

Question 24

Why does the fetus still exist at a low pO2 (no more than 30) even after the initial hypoxic stage?

Answer 24

To protect from oxidative stress (more pCO2)

Question 25

Describe the placental gas exchange gradient

Answer 25

Big gradient from mother to baby

Question 26

Does maternal and fetal blood have the same or different buffer?

Answer 26

Same - placenta controls the pH of placental blood via bicarbonate buffer (acid base balance)

Question 27

What is a big reason for SGA at birth?

Answer 27

Lack of transport of amino acids due to gene problems with transporters

Question 28

Is there a net transport of amino acids to the fetus?

Answer 28

Yes

Question 29

Why in developing countries do we want to improve the nutrition of mother before she conceives?

Answer 29

To prevent fetal growth restriction (FGR) → main problem is issue with placenta e.g. anaemia and protein deficiency

Question 30

What does there need to be for implantation to happen?

Answer 30

Low oxygen tension

Question 31

What would a gap in the placenta on US suggest?

Answer 31

Bleeding

Question 32

What happens to the placenta in pre-eclampsia and FGR?

Answer 32

1) Placental villous tree has fewer branches bc of altered blood flow characteristics
2) Spiral artery remains narrowed

Question 33

What is PI on a uterine artery doppler?

Answer 33

(Vmax-Vmin)/Vmax mean

Question 34

What does increased PI increase the risk of?

Answer 34

Severe pre-eclampsia

Question 35

When is severe IUGR best predicted in low-risk patients?

Answer 35

Second trimester by an increased PI

Question 36

Can you pick up people likely to have a PE early (at 14 weeks)?

Answer 36

Yes but can’t prevent it - looks like a non-pregnant scan

Question 37

What are monozygotic twins?

Answer 37

From one egg, identical (incidence = 3:1000 deliveries)

Question 38

What are dizygotic twins?

Answer 38

Two eggs, non-identical (incidence of spontaneous dizygotic twins = 1:80)

Question 39

What are risk factors for dizygotic twins?

Answer 39

1) Peak age 35-40 years - FSH rises, biological advantage of double ovulating, more chance of at least one succeeding
2) FH
3) Previous multiple birth
4) Increased BMI
5) Parity
6) Summer and autumn conceptions
7) Smoking
8) COCP

Question 40

What are the three types of monozygotic twins (can see on US)?

Answer 40

1) Dichorionic, diamniotic - cleavage before implantation, two placentas, two amniotic sacs
2) Monochorionic, diamniotic - cleavage at day 6-8, one placenta, two amniotic sacs
3) Monochorionic, monoamniotic - cleavage after day 8, one placenta, one amniotic sac, 4%

Question 41

What causes conjoined monozygotic twins?

Answer 41

Divide of placenta happens even later

Question 42

What increases the risk of monozygotic twins?

Answer 42

IVF

Question 43

What type of twins can be dichorionic and what type can be monochorionic?

Answer 43

1) Dichorionic - can be monozygotic or dizygotic

2) Monochorionic - can only be monozygotic

Question 44

What is the most common combination for triplets?

Answer 44

Pair of monozygotic twins and a dizygotic