Repo 8: Pregnancy

Question 1

What happens to the yolk sac as the foetus grows?

Answer 1

Yolk sac disappears as the amniotic sac enlarges due to growth of the foetus
So chorionic sac is occupied by the expanding amniotic sac

Question 2

What is meant by the term haemomonochorial?

Answer 2

That only one single trophoblast layer separates maternal blood from foetal capillary blood
The two circulations never mix!

Question 3

What are chorionic villi?

Answer 3

Finger like projections that the Charon forms

They represent the point of exchange between the maternal and foetal circulations

Question 4

What is an ectopic pregnancy?

Answer 4

Implantation at a site other the the uterine body, often in the Fallopian tube

Question 5

What is placenta praevia?

Answer 5

Implantation int eh lower uterine segment that can cause haemorrhage in pregnancy
Requires a c-section as the birth canal is obstructed

Question 6

Which cells in the endometrium prepare for implantation?

Answer 6

Pre-decidual cells

Question 7

How must the flow and resistance of the blood supply in the endometrium adapt for pregnancy?

Answer 7

Spiral artery remodelling
To create a high flow and low resistance blood supply

(This does not happen in pre-eclampsia)

Question 8

Which layer of trophoblast impedes the mother?

Answer 8

Cytotrophoblast (lined with syncytiotrophoblast)

Question 9

How does the barrier of the placenta change over the course of pregnancy?

Answer 9

Barrier is thick in first trimester (OK as demands of foetus are fairly low)
As placenta matures to meet increasing foetal demands, is decreased the interhaemal distance by thinning the trophoblast layers (now just syncytiotrophoblast) and increasing the SA for exchange through branching of the villus tree

Question 10

Which vessels carry oxygenated and deoxygenated blood to the foetus?

Answer 10

2 umbilical arteries carry deoxygenated blood from foetus to placenta
1 umbilical vein carries oxygenated blood from placenta to foetus

Question 11

What is the function of hCG?

Answer 11

Produced in first 2 months of pregnancy to support CL

Excreted in maternal urine (used for pregnancy testing)

Question 12

Which trophoblast layer secretes hCG?

Answer 12

Syncytiotrophoblast

Question 13

Which steroid hormones does the placenta produce?

Answer 13

Progesterone and oestrogen

Responsible for maintaining pregnancy state (progesterone increases maternal appetite to lay down fats for late pregnancy)
Placenta takes over CL production by 11th week

Question 14

What is the main function of hPL?

Answer 14

Increases glucose availability to foetus

Question 15

Give an example of molecules that are transported across the placenta by simple diffusion, facilitated diffusion, active transport, and receptor mediated transport.

Answer 15

Simple diffusion: water, urea, electrolytes, gases
Facilitated diffusion: glucose
Active transport: AAs, iron, vitamins
Receptor mediated transport: IgG

Question 16

How does the foetus develop passive immunity?

Answer 16

IgG transported from mother to foetus by receptor mediated transport

Question 17

What is haemolytic disease of the newborn?

Answer 17

Rheus blood group incompatibility between mum and foetus
So mums IgG transports across placenta and binds to antigens on foetal RBCs and attacks them, causing haemolysis

Now uncommon because of prophylactic treatment

Question 18

How does alcohol cross the placenta and what implications does this have for the development of a baby whose mother drinks during pregnancy?

Answer 18

By diffusion because it’s lipid soluble
Can cause foetal alcohol syndrome causing foetus of low weight and with growth retardation and head and facial abnormalities

Question 19

How does CO, SV and HR alter with pregnancy?

Answer 19

All increase

Question 20

Why does systemic vascular resistance decrease in pregnancy?

Answer 20

Due to progesterone relaxing smooth muscle

Question 21

How does blood pressure change along the course of pregnancy?

Answer 21

In T1 and T2, blood pressure drops (due to progesterone systemic vascular resistance) then returns to normal in T3 due to aortocaval compression by Gracie uterus

Question 22

How does the renal system change in pregnancy?

Answer 22

GFR increases (possibly due to progesterone acting on glomerular arterioles)
Creatine, protein and urea excretion all increase so are lower in mother

Question 23

Why are pregnant women at increased risk of UTIs?

Answer 23

Due to urinary stasis brought about by hydroureter (dilated ureter due to progesterone), and obstruction by compression of gravid uterus

Question 24

How does pregnancy alter maternal respiration?

Answer 24

Diaphragm displaced by gravid uterus
But AP and transverse diameters of thorax increase

Tidal volume increases but RR unchanged
O2 consumption increases

Question 25

How is vital capacity unchanged in pregnancy?

Answer 25

Even thought tidal volume increase, this means expiratory reserve volume decreases

Question 26

How is pH altered in pregnancy?

Answer 26

State of compensated respiratory alkalosis due to decrease on arterial pCO2, which is compensated by increased renal bicarbonate excretion

Question 27

How does carbohydrate metabolism change in pregnancy?

Answer 27

Glucose is supplied to the foetus by facilitated diffusion across the placenta Mother develops insulin resistance during second half of pregnancy so switches to gluconeogenesis and use of alternative fuels (FAs, ketones, triglycerides) which is achieved by hPL

Question 28

What are the risks for the foetus if the mother develops gestational diabetes?

Answer 28

Macrosomic foetus Congenital defects Still birth

Question 29

How does lipid metabolism change in pregnancy?

Answer 29

From T2 there is increased lipolysis so more free FAs | FAs don't cross the placenta so are reserved for maternal metabolism, leaving glucose for the foetus

Question 30

How do levels of thyroid hormones change throughout pregnancy?

Answer 30

TBG increases Levels of T3 and T4 increases but T4 still in normal range due to increased TBG hCG has effect to raise TSH, but not significantly (Huge rise in TSH may indicate iodine deficiency of hypothyroidism)

Question 31

Where does the appendix move to in pregnancy?

Answer 31

RUQ, due to enlargement of uterus

Question 32

How is the GI system affected by pregnancy?

Answer 32

Smooth muscle relaxation due to progesterone, hence... - heartburn (relaxed lower oesophageal sphincter enables reflux) - constipation (slower transit time to allow more nutrient absorption) - gallstone (due to stasis in biliary tree) - risk of pancreatitis due to hyperlipidaemia of pregnancy

Question 33

How does pregnancy affect maternal haematology?

Answer 33

Pregnancy is a pro-thrombotic state (to prepare for blood loss at parturition) Increased levels of fibrinogen and clotting factors, and reduction of fibrinolysis

Question 34

Why could anaemia form in pregnancy?

Answer 34

- due to Fe and folate deficiency | - or dilutional anaemia due to increase in plasma volume but little increase in RBCs

Question 35

Why could warfarin not be prescribed to a pregnant women with thromboembolic disease?

Answer 35

As warfarin is a teratogen and can cross the placenta

Question 36

How does the maternal immune system change in pregnancy?

Answer 36

- foetus is an allograft so there is suppression of immune response at maternal-foetal interface - mum also supplied IgG to foetus across placenta (*Rheus incompatibility*)

Question 37

Why would there be a concern if a pregnant woman had Graves/ Hashimoto's?

Answer 37

These are autoimmune diseases, so it is possible these antibodies could transfer from the mum to the foetus and have the same affect on it