Placenta And Maternal Problems Flashcards
The outer cell mass turns into …
Syncytiotrophoblast
Cytotrophoblast
The inner cell mass turns into…
Epiblast
Hypoblast
Which tissues form the bilaminar disk?
Epiblast and hypoblast
Describe the syncytiotrophoblast
Multinucleated sheet
Well adapted for transport
Minimal cellular barriers
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
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
What anchors the placenta in position?
Establishment of an outermost cytotrophoblast shell
What is the cytotrophoblast layer for?
Stem cell layer for the syncytiotrophoblast
What is the most common site of ectopic pregnancy?
Ampulla of Fallopian tubes
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
What are pre-decidual cells?
Cells specialised to control implantation
Why doesn’t implantation in the Fallopian tubes work?
No pre-decidual cells as no endometrium in tubes
Cannot control implantation
Risk of haemoperitoneum
What is the basic pathology of pre-eclampsia?
Invasion is incomplete
Inadequate modification of vessel walls
What are the 2 clinical signs of pre-eclampsia?
Hypertension
Proteinuria
Describe a first trimester placenta
Placenta established
Placental barrier still relatively thick
Complete cytotrophoblast layer beneath syncytiotrophoblast
Describe a placenta at term
Increased SA for exchange - optimised for transport
Placental barrier is now thin
Cytotrophoblast layer lost
How many umbilical arteries are there and carrying what?
2
Deoxygenated blood
How many umbilical veins are there and carrying what?
1
Oxygenated blood
What are the steroid hormones produced by the placenta?
Oestrogen
Progesterone
What are the protein hormones produced by the placenta?
hCG
hCS
hCT
hCC
What is a molar pregnancy?
Abnormal growth of pregnancy tissue
Placental overgrowth
Massive overproduction of hCG
What crosses the placenta via simple diffusion?
Water
Electrolytes
Urea and uric acid
Gases
What crosses the placenta via facilitated diffusion?
Glucose
What needs active transport to cross the placenta?
Amino acids
Iron
Vitamins
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?
No
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?
No
Is functional residual capacity changed in pregnancy?
Yes
Decreased but only in T3
Is vital capacity changed in pregnancy?
No
Is FEV1 changed in pregnancy?
No
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)
