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8) Pregnancy Flashcards

1
Q

On what day does the blastocyst implant into the endometrium of the uterine cavity?

A

Day 6 (after fertilisation)

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2
Q

What does further embedding of the blastocyst into the endometrium rely on?

A

Invasive property of trophoblast cells
Outer layer of syncitiotrophoblast
Underlying cytotrophoblast

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3
Q

By what day is the blastocyst fully embedded within the endometrium?

A

10th day after fertilisation

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4
Q

Implantation is interstitial, what does this mean?

A

Uterine epithelium is breached & conceptus implants within stroma

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5
Q

The placenta is haemomonochorial. What does this mean?

A

One layer of trophoblast separates maternal blood from foetal capillary wall

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6
Q

What are the aims of implantation?

A

Establish the basic unit of exchange (Primary, secondary & tertiary villi)
Anchor the placenta
Establish maternal blood flow within the placenta

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7
Q

What are the differences between primary, secondary & tertiary villi in the conceptus?

A

Primary villi - early, finger-like projections of trophoblast (day 13)
Secondary villi - Invasion of mesenchyme into core (day 15-16)
Tertiary villi - Invasion of mesenchyme core by foetal vessels (day 23)

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8
Q

How is the endometrium of the uterus prepared for implantation?

A

Decidualisation

Remodelling of spiral arteries

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9
Q

What is decidualisation (of the uterine endometrium)?

A

Pre-decidual cells
Decidual reaction provides balancing force for the invasive force of the trophoblast
Stimulated by progesterone
Without balancing force complications e.g. haemorrhage

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10
Q

How are the spiral arteries of the endometrium remodelled in preparation for implantation?

A

Creation of low resistance vascular bed

Maintains high flow required to meet foetal demand particularly late in gestation

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11
Q

What implantation defects can occur?

A 
Ectopic pregnancy (most commonly F. tube)
Placenta praevia
Incomplete invasion (placental insufficiency, pre-eclampsia)
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12
Q

What is placenta praevia?

A

Implantation in the lower uterine segment
Can cause haemorrhage in pregnancy
Requires C-section delivery

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13
Q

Describe the structure of the placenta by the beginning of the 4th month

A
  1. Foetal portion
    Formed by chorion frondsum, bordered by chorionic plate
  2. Maternal portion
    Formed by the decidua basalis
    The decidual plate is most intimately incorporated into placenta
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14
Q

In the placenta, what lies between the chorionic & decidual plates?

A

Intervillous spaces

Filled with maternal blood

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15
Q

During the 4th & 5th months, what happens to the placenta?

A

Decidua form decidual septa
Septa project into intervillous spaces but don’t reach chorionic plate
Septa divide placenta into compartments - Cotyledons

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16
Q

Throughout pregnancy how much of the uterus does the placenta cover?

A

15-30% of the internal surface of the uterus

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17
Q

Describe the first trimester placenta

A

Placenta established
Placental ‘barrier’ to diffusion still relatively thick
Complete cytotrophoblast layer beneath syncytiotrophoblast

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18
Q

Describe the placenta at term

A

Surface area for gas exchange dramatically increased
Placental ‘barrier’ now thin
Cytotrophoblast layer beneath syncytiotrophoblast lost

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19
Q

Describe the arrangement of foetal blood vessels within the placenta

A

Umbilical arteries & veins project into tertiary villi
Tertiary villi bathed in oxygenated maternal blood
2 Umbilical arteries
- Deoxygenated blood foetus > placenta
1 umbilical vein
- Oxygenated blood placenta > foetus

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20
Q

How do cotyledons receive their blood supply?

A

80-100 spiral arteries pierce decidual plate
Pressure forces oxygenated blood deep into intervillous spaces, bathes small villi
As pressure decreases, blood flows back from chorionic plate towards decidua, enters endometrial veins

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21
Q

What factors influence the passive diffusion of substances across the placenta?

A

Concentration gradient
Barrier to diffusion (placental membrane thins as foetal demands increase)
Diffusion distance (haemomonochorial)

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22
Q

Which substances are transported across the placenta?

A 
- Simple diffusion
water, electrolytes, urea & uric acid gases (flow-limited)
 - Facilitated diffusion
Glucose
 - Active transport
Amino acids, iron, vitamins
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23
Q

What are teratogens?

A

Substances or environmental agents which cause the development of abnormal cell masses during foetal growth, resulting in physical defects in the foetus

24
Q

Name some common teratogens

A 
Thalidomide
Alcohol
Therapeutic drugs
Drugs of abuse
Maternal smoking
25
Q

Which pathogens are able to cross the placenta?

A 
Varicella zoster
Cytomegalovirus
Treponema pallidum
Toxoplasma gondii
Rubella
26
Q

What hormones does the placenta produce?

A 
Protein hormones
 - Human chorionic gonadotrophin (hCG)
 - Human chorionic somatomammotrophin (hCS)
 - Human chorionic thyrotrophin
 - Human chorionic corticotrophin
Steroids
 - Progesterone
 - Oestrogen
27
Q

What is hCG?

A

Human chorionic gonadotrophin
Produced during first 2 months of pregnancy
Supports the secretory function of the CL
Produced by syncytiotrophoblast so pregnancy specific

28
Q

What is the function of human chorionic somatomammotrophin?

A

Influences maternal metabolism

Increases availability of glucose to foetus

29
Q

During pregnancy where is progesterone produced?

A

Corpus luteum up to week 11
Placenta takes over production

Influences maternal metabolism, increased appetite

30
Q

Apart from protein & steroid hormones, what else does the placenta synthesise?

A

Glycogen
Cholesterol
Fatty acids

31
Q

Describe how pregnancy tests work

A

Tests hCG
hCG produced in first 2 months of pregnancy
Produced by syncytiotrophoblast so pregnancy specific
Excreted in maternal urine

32
Q

What type of immunity can the placenta provide the neonate with?

A

Passive immunity
Foetal immunoglobulins consist almost entirely of maternal immunoglobulin (IgG)
Mother > Foetus around week 14
Receptor mediated pinocytosis
Eventually foetal plasma IgG exceeds maternal

33
Q

How may a newborn contract a haemolytic disease from its mother?

A

Rhesus blood group incompatibility
Mother previously sensitised to rhesus antigen (previous pregnancy)
IgG against rhesus crosses placenta & attacks foetal RBCs
Now uncommon due to prophylaxis

34
Q

What prophylactic treatment is there for haemolytic disease of the newborn?

A

Rhesus -ve mothers pregnant with rhesus +ve foetus given specific IgG throughout pregnancy (anti-D)
Prevent sensitisation if exposed to antigen
(IgG binds to antigen before mother’s immune system can mount a response)

35
Q

Physiological changes take place in which main systems of the body during pregnancy?

A 
CVS
Urinary
Respiratory
GI
Immune
Metabolic changes - carbohydrate, thyroid hormones
36
Q

What maternal physiological changes take place in the Cardiovascular system during pregnancy?

A 
CO increases 40%
SV increases 35%
HR increases 15%
Blood volume increases
Systemic vascular resistance decrease 25-30%
37
Q

What happens to maternal BP during pregnancy?

A

Hypotension T1 &T2 (progesterone effects on systemic vascular resistance)
Returns to normal T3 (aortocaval compression by gravid uterus)
Systolic BP never normally increased in pregnancy

38
Q

What maternal physiological changes take place in the Urinary system during pregnancy?

A

Renal plasma flow (60-80%) & GFR (55%) increase
Creatinine clearance & protein excretion increase
Plasma urea, uric acid, bicarbonate & creatinine decrease

39
Q

Urinary stasis can occur during pregnancy. How?

A

Progesterone relaxes the smooth muscle in walls of ureters

Can cause stastis, hydroureter, UTIs, pyelonephritis - can induce pre-term labour

40
Q

What maternal physiological changes take place in the Respiratory system during pregnancy?

A

Diaphragm displaced
A-P & transverse diameters of thorax increase
O2 consumption increases (20%)
Resting minute ventilation & Tidal volume increase
Respiratory rate, VC & FEV1 unchanged
Functional residual capacity decreased (T3)

41
Q

What happens to the acid-base balance of the mother during pregnancy?

A

Physiological hyperventilation driven by progesterone
Allows mother to blow off extra CO2 produced by foetus
Respiratory Alkalosis
Kidneys compensate, produce & reabsorb less HCO3-

42
Q

What maternal changes take place with carbohydrate metabolism during the first half of pregnancy?

A

Foetal supply of glucose & a.a. favoured
Fat laid down in 1st half of pregnancy helps meet later foetal demands
Progesterone stimulates appetite & diverts glucose into fat synthesis
Oestrogen stimulates prolactin release, generates maternal resistance to insulin
Maternal glucose usage declines, gluconeogenesis increases, maximises availability of glucose to foetus

43
Q

What maternal changes take place with carbohydrate metabolism during the second half of pregnancy?

A

Mother’s energy needs met by metabolising peripheral fatty acids
Placental transport of glucose (facilitated diffusion)
Increased maternal peripheral insulin resistance (switch to gluconeogenesis & other fuels)
Achieved by human placental lactogen (prolactin, oestrogen/progesterone & cortisol)
Decreased fasting blood glucose
Increase in post-meal (post-prandial) blood glucose

44
Q

What is gestational diabetes?

A

Carbohydrate intolerance first recognised in pregnancy and does not persist after delivery
Oral glucose tolerance test required
Pancreas unable to respond to metabolic demand of pregnancy, blood glucose increases
When demands removed, pancreas can respond adequately again

45
Q

What risks are associated with poor control of gestational diabetes?

A

Macrosomic foetus
Stillbirth
Increased risk of congenital heart defects

46
Q

How does the pancreas usually cope with the increased demand for insulin during pregnancy?

A

Basal & stimulated insulin normally increases as pregnancy proceeds
Beta-cell hyperplasia & hypertrophy
Increased rate of insulin synthesis in the beta-cells

47
Q

What maternal changes take place regarding lipid metabolism during pregnancy?

A

Increase in lipolysis from T2
Increase in plasma [free fatty acids] on fasting (fatty acids for mum, glucose for foetus)
Increased utilisation of free fatty acids increases risk of ketoacidosis (may combine with compensated resp alkalosis = very bad!)

48
Q

What maternal changes take place regarding the thyroid during pregnancy?

A

Thyroid binding globulin production increased
T3 & T4 increased
Free T4 in normal range due to increased binding globulin

49
Q

What effect does hCG have on the thyroid during pregnancy?

A

Direct effect
Stimulates T3 & T4 production
TSH can be decreased in normal pregnancies due to -ve feedback from T3 & T4 produced due to hCG secretion

50
Q

What maternal physiological changes take place in the Gastrointestinal system during pregnancy?

A

Anatomical - alterations in position of viscera (appendix moves RLQ > RUQ as uterus enlarges)
Physiological - Smooth muscle relaxation (progesterone), GI delayed emptying, Biliary tract stasis, Increased risk of pancreatitis

51
Q

Pregnancy is a pro-thrombotic state. What consequences does this have?

A

High amount of fibrin deposition at site of implantation
- Increased fibrinogen & clotting factors
- Reduced fibrinolysis
Stasis, venodilation
Results in thromboembolic disease in pregnancy
- Cannot give warfarin (teratogenic)

52
Q

What type of anaemia can occur during pregnancy?

A

Physiological anaemia
- not true anaemia, mis-match between volume & haemocrit
Plasma volume increases
RBC mass also increases, not to same degree
Anaemia due to Fe and folate deficiency can also occur

53
Q

What maternal physiological changes take place in the Immune system during pregnancy?

A

Foetus = allograft (genetically different to mother)
Non-specific suppression of local immune response at materno-foetal interface
Transfer of antibodies IgG
Haemolytic disease - ABO antibodies don’t cross, Rhesus antibodies do
Graves/Hashimoto’s thyroiditis - Antibodies cross placenta, stimulate TSH receptors or destroy foetal thyroid

54
Q

What is the purpose of antenatal screening?

A

History & examination - risk factors e.g. gestational diabetes
Blood test - Blood group, Hb, Infection
Urinalysis - Protein

55
Q

What changes occur during a pre-eclamptic pregnancy?

A 
Vasoconstricted
Plasma - contracted
Raised BP
Proteinuria
Pitting oedema

Reproduction (13 decks)

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