Placenta And Maternal Problems Flashcards by Maya White

The outer cell mass turns into …

Syncytiotrophoblast

Cytotrophoblast

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The inner cell mass turns into…

Epiblast

Hypoblast

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Which tissues form the bilaminar disk?

Epiblast and hypoblast

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Describe the syncytiotrophoblast

Multinucleated sheet
Well adapted for transport
Minimal cellular barriers

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What do we mean when we say the human placenta in haemomonochorial?

One layer of trophoblast ultimately separates the maternal blood from the foetal capillary wall

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Describe the chorionic villi as development proceeds

Primary - early finger-like projections of trophoblast
Secondary - invasion of mesenchyme into core
Tertiary - invasion of mesenchyme core by foetal vessels

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What anchors the placenta in position?

Establishment of an outermost cytotrophoblast shell

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What is the cytotrophoblast layer for?

Stem cell layer for the syncytiotrophoblast

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What is the most common site of ectopic pregnancy?

Ampulla of Fallopian tubes

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What is placenta praevia?

Implantation in the lower uterine segment
Can cause haemorrhage in pregnancy
Requires C section
May grow across internal Os then birth canal cannot function

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What are pre-decidual cells?

Cells specialised to control implantation

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Why doesn’t implantation in the Fallopian tubes work?

No pre-decidual cells as no endometrium in tubes
Cannot control implantation
Risk of haemoperitoneum

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What is the basic pathology of pre-eclampsia?

Invasion is incomplete

Inadequate modification of vessel walls

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What are the 2 clinical signs of pre-eclampsia?

Hypertension

Proteinuria

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Describe a first trimester placenta

Placenta established
Placental barrier still relatively thick
Complete cytotrophoblast layer beneath syncytiotrophoblast

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Describe a placenta at term

Increased SA for exchange - optimised for transport
Placental barrier is now thin
Cytotrophoblast layer lost

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How many umbilical arteries are there and carrying what?

Deoxygenated blood

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How many umbilical veins are there and carrying what?

Oxygenated blood

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What are the steroid hormones produced by the placenta?

Oestrogen

Progesterone

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What are the protein hormones produced by the placenta?

hCG
hCS
hCT
hCC

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What is a molar pregnancy?

Abnormal growth of pregnancy tissue
Placental overgrowth
Massive overproduction of hCG

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What crosses the placenta via simple diffusion?

Water
Electrolytes
Urea and uric acid
Gases

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What crosses the placenta via facilitated diffusion?

Glucose

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What needs active transport to cross the placenta?

Amino acids
Iron
Vitamins

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Describe passive immunity in babies

Foetal immune system immature Receptor mediated endocytosis allowing IgG to cross placenta Foetus likely to encounter same agents as mother

Describe haemolytic disease of the newborn

Rhesus blood group incompatibility of foetus and mother Mother makes antibodies that attack foetal blood Mothers given prophylactic anti-D treatment

Name some infectious agents that can cross the placenta

Varicella zoster Cytomegalovirus Treponema pallidum (syphilis) Rubella

What do you test for in mother's blood at antenatal screening?

Blood group - Rhesus status Hb Infections

What do we check mother's urine for at antenatal screening?

Signs of infection | Protein

By how much does blood volume change in pregnancy?

Increases | ~50%

Why does maternal blood volume increase in pregnancy?

Increased blood to kidneys as acting for foetus and mother | In anticipation of blood loss of birth

How much blood is typically lost at birth?

500 ml - normal delivery | 1 L - C section

By how much does cardiac output change in the mother?

Increases | ~ 40%

By how much does stroke volume change in the mother?

Increased | ~35%

By how much does heart rate change in the mother?

Increases | ~15%

What is the change to TPR in the mother and how?

Decreases 25-30% High conc of progesterone relaxes the SM

What happens to BP of the mother during pregnancy?

T1 and T2 = decreased | T3 = returns to normal

Is there any time when systolic BP naturally increases in pregnancy?

Why might hypotension occur in pregnancy?

T1 and T2 = increased progesterone therefore decreased TPR | T3 = aortocaval compression by gravid uterus

Describe what is happening histologically in a pre-eclamptic pregnancy

Vasoconstriction Plasma contracted - decreased volume Opposite of what is needed therefore strain on placental and foetal demands

What is eclampsia?

Fits/seizures in pregnancy | Emergency situation

How does renal plasma flow change during pregnancy?

Increases | 60-80%

How does GFR change in pregnancy?

Increases | 55%

How does creatinine clearance change in pregnancy?

Increases 40-50% Therefore creatinine itself decreases

What happens to urea conc in pregnancy?

Decreases | 50%

What happens to uric acid conc in pregnancy?

Decreases | 33%

What is the range for bicarbonate during pregnancy?

18 - 22 mmol/L

What is the range for creatinine during pregnancy?

25 - 75 mmol/L

Why might urinary stasis occur in pregnancy?

Progesterone relaxes SM May cause hydroureter or hydronephrosis Or could be due to obstruction secondary to gravid uterus

What is a potential complication of pyelonephritis for pregnancy women?

Pre term labour

What is the effect of progesterone on the respiratory system?

Increased respiratory drive | Can result in resp alkalosis

Why is there an increased risk of developing metabolic acidosis whilst pregnant?

Buffering capacity is reduced as there is chronic loss of bicarbonate during pregnancy

How does oxygen consumption change in pregnancy?

Increased | 20%

How does resting minute ventilation change in pregnancy?

Increased | 15%

Is tidal volume changed in pregnancy?

Yes - increased

Is respiratory rate changed in pregnancy?

Is functional residual capacity changed in pregnancy?

Yes | Decreased but only in T3

Is vital capacity changed in pregnancy?

Is FEV1 changed in pregnancy?

Is maternal ppO2 changed in pregnancy?

Yes - increased

Is maternal ppCO2 changed in pregnancy?

Yes - decreased

How does pregnancy change maternal use of carbohydrates?

Increased maternal peripheral resistance to insulin Switches to gluconeogenesis and alternative fuels (FAs) Via human placental lactogen (hPL)

What is gestational diabetes?

Carbohydrate intolerance first recognised in pregnancy and not persisting after delivery

What are the risks of gestational diabetes?

Macrosomia (C section?) Stillbirth Increased risk of congenital defects

How do we test for gestational diabetes?

Oral glucose tolerance test

Describe lipid metabolism during pregnancy

Early pregnancy = increased fat stores Increased lipolysis from T2 Increased plasma free FAs on fasting

Can FAs cross the placenta?

Only the essential FAs

How is the thyroid affected in pregnancy?

Increased production TBG Increased release of T3 and T4 Free T4 in normal range as most is bound

What foetal hormone has a direct effect on TSH production?

hCG

What happens to the appendix in pregnancy?

Gets moved to RUQ as uterus enlarges

What physiological changes occur in the GI tract whilst pregnant?

SM relaxation causes delayed emptying/nausea etc and biliary tract stasis Changes in bile salt composition - increased risk of stones Increased risk of pancreatitis

Why is pregnancy a pro-thrombotic state?

Lots of fibrin deposition at implantation site Increased fibrinogen and clotting factor production Reduced fibrinolysis (Plus stairs and venodilation)

Why can we not give warfarin during pregnancy?

It crosses the placenta | Is teratogenic

What is the change to plasma volume in pregnancy?

Increases 40-50%

What is the change to red cell mass in pregnancy?

Increased | 20-30%

Why is maternal physiological anaemia common?

There are fewer RBCs relative to the volume of plasma

Apart from physiological anaemia, which other types of anaemia are most common with pregnancy?

Folate deficiency | Iron deficiency

What do we mean by 'the foetus is an allograft'?

Genetically distinct to the mother | Will express some HLA antigens from the father (that the mother does not have)