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Year 2 - T2 Theme 2 > L18 Physiology of pregnancy > Flashcards

L18 Physiology of pregnancy Flashcards

1
Q

What is there an increase in physiological demand for by the foetus during pregnancy

A
  • Nutrients(eg. O2, amino acids, glucose)
  • Amniotic fluid production
  • Removal of foetal waste products(eg CO2, nitrogen compounds)

Requires increased:

  • Nutrient content (gastro intestinal)
  • Oxygen content (pulmonary and cardiovascular)
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2
Q

How much does plasma volume increase by during volume homeostasis

A
  • A rapid increase in plasma volume by 40%
  • Plasma colloid osmotic(oncotic) pressure falls –> causes a shift of fluid into extra cellular space, increased hydration of connective tissue and oedema(lower limbs, hands and face)
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3
Q

Mechanism of increased plasma volume

A
  • Slight decrease atrial natriuretic peptide (ANP)
  • Decreased thirst threshold (increased fluid intake)
  • Re-setting osmostat
  • Increased plasma volume
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4
Q

Changes in haemoglobin levels during pregnancy

A
  • Red cell mass increased by 25%
  • Plasma volume increased by 40%
  • Dilutional anaemia
  • Iron is required for the increased red cell mass(fall in ferritin levels, increased iron absorption from gut)
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5
Q

Is Fe supplementation required for twins

A
  • No need for routine Fe supplementation except for twins
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6
Q

Changes in uterine blood flow

A
  • Uterine blood flow increases 3.5 fold from 95 to 342 ml/min
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7
Q

Features of haemostasis

A
  • Hypercoagulable state - increase plasma fibrinogen(increased ESR), platelets, factor VIII and von willebrand factor
  • Marked effect at delivery - 500ml/min blood loss at placental separation, myometrial contraction(10% of all fibrinogen used up)
  • Evolutionary balance between thrombosis and haemorrhage
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8
Q

Changes in white blood cell levels during pregnancy

A
  • Concentration does not fall during pregnancy
  • Total WBC increases in pregnancy
  • Increase in neutrophils(reduced apoptosis)
  • Marked increased around delivery
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9
Q

Implications of increased blood volume on the CVS

A

Increased blood volume has implications on:

  • Cardiac output
  • Peripheral resistance
  • Blood pressure
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10
Q

Changes in the heart during pregnancy

A
  • Heart enlarges by 12% (increased venous return)
  • Innocent systolic murmurs are common(-90%)
  • Diastolic murmurs(-20%) - require investigation ro rule out other pathologies
  • Uterus pushing up against the diaphragm can cause the maternal heart to shift up in the chest cavity
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11
Q

Other pathologies that may cause diastolic murmurs

A
  • May be innocent - reflecting increased flow across atrioventricular valves
  • Will require further investigation to rule out cardiopathies - but be aware… change in cardiac axis/position result in changes on ECG and x-ray
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12
Q

Changes in peripheral resistance during pregnancy

A
  • Peripheral vasodilatation (effect of progesterone)

- Peripheral resistance decreases by 35%

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13
Q

What is the decrease in peripheral resistance partly compensated by

A
  • Decrease in resistance is partly compensated by an increase in cardiac output which results in a small change in BP
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14
Q

What is increased pulmonary blood flow during pregnancy matched by

A
  • Increase in tidal flow
  • Decrease in maternal pCO2 and increase in maternal pO2
  • Increased availability of O2 to tissues and aids passive diffusion at the placenta i.e higher concentration gradient
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15
Q

Effects of cardiovascular and respiratory changes

A
  • High blood flow maximises pO2 on maternal side of the placenta
  • Foetal haemoglobin(HbF) has a higher affinity for O2 compared with maternal adult Hb(HbA)
  • Increased cardiac output may increase flow in skin aiding heat loss (high metabolic state)
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16
Q

Changes in the renal system during pregnancy

A
  • Kidney increases 1cm in size during pregnancy
  • GFR and effective renal plasma flow increase 50+%
  • But tubular reabsorption capacity is unchanged –> leads to a decrease in glucose reabsorption thus glycosuria is common
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17
Q

Changes in plasma levels of creatinine and urea

A
  • Plasma levels of creatinine and urea decrease in pregnancy

- All the increments are present by the second trimester

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18
Q

Change in GFR during the third trimester

A
  • Reduction GFR of 15% during the third trimester
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19
Q

Changes in renal pelvis and ureters

A
  • Dilatation of renal pelvis and ureters (progesterone) - increased urinary tract infections in pregnancy
20
Q

Changes in GI system

A
  • Gastro-oesophageal reflux up to 70%

- Slowing of gut motility and constipation (progesterone effect)

21
Q

Why is there an increase in gastro-oesophageal reflux during pregnancy

A
  • Due to increase in abdominal pressure, reduced pyloric sphincter with back wash of bile secondary to hormonal changes
  • Simple measures - avoidance of fat and alcohol
  • Upright posture and antacids
22
Q

Glucose metabolism - first trimester

A
  • Increased sensitivity to insulin thus mothers increase glycogen synthesis and fat deposition
23
Q

Glucose metabolism - second trimester

A
  • Insulin resistance
  • Cortisol, progesterone, HPL, and oestrogen are all insulin antagonists
  • Thus glucose levels may rise and there is an increase in fatty acids(another source of energy for the fetus)
24
Q

Why is folate important

A
  • DNA synthesis, repair and regulation
  • RBC development
  • Plasma folate represents current nutritional status, but
  • Significant tissue stores(eg liver) - RBC folate is a good biomarker(no change in pregnancy) –> dietary deficiency can take months to become significant
  • No need for folate supplementation but prevents neural tube defects thus routinely given preconception to 3 months
25
Q

Why is folate important for DNA synthesis, repair and regulation

A
  • Important in rapid cell division (embryos)

- Deficiency in pregnancy associated with neural tube defects (NTDs)

26
Q

What type of anaemia can result from folate deficiency

A
  • Macrocytic anaemia
27
Q

Changes in thyroid function - pregnancy

A
  • Increased iodine absorption
  • Increased serum T3 and T4 levels
  • Increase in thyroid binding globulin(oestrogen)
  • As only unbound T3 and T4 is active, levels of free T3 and T4 remain the same or fall slightly
  • In general, thyroid function remains unchanged
  • if hypothyroid may need to increase dose due to increased TBG levels
28
Q

Protein hormones produced by the placenta

A
  • hCG
  • hPL
  • hPG
  • CRH
29
Q

Steroids produced by the placenta

A
  • Progesterone

- Oestrogen(oestriol)

30
Q

When is hCG first detectable

A
  • First detectable 8-9 days after ovulation and peaks at 8-10 weeks
31
Q

Which subunit from hCG is used as the pregnancy test

A
  • Beta subunit is used as the pregnancy test
32
Q

Changes in hCG levels during pregnancy

A
  • Doubles every 48-72 hours
33
Q

What layer of the embryo produces hCG

A
  • Produced by the trophoblast

- Produced in large quantities by hydatidiform molar pregnancy and choriocarcinoma

34
Q

When are hCG levels usually lower during a pregnancy

A
  • Usually significantly lower in ectopic pregnancy and risk of miscarriages
35
Q

What is the alpha subunit of hCG similar to

A
  • Alpha subunit very similar to LH, FSH, TSH

- Has LH type properties but longer half life (24 h)

36
Q

effects of hCG

A
  • Maintains corpus luteum secretion of progesteron and oestrogen
  • Decreases as the placental production of progesterone increases
  • Later in pregnancy may have a role in maternal oestrogen secretion and modulation of the maternal immune response
37
Q

What is hPL similar to

A
  • Similar structure to prolactin and growth hormone
38
Q

Link between placenta size and hPL levels

A

The bigger the placenta, the more hPL

39
Q

Half life of hPL

A

Half life - 30 mins

40
Q

Effects of hPL

A

Alters maternal carbohydrate and lipid metabolism to provide for foetal requirements

  • Mobilising maternal free fatty acids
  • Inhibits maternal peripheral uptake of glucose
  • Increases insulin release from pancreas

Aim is a steady state of glucose for the fetus

41
Q

Effects of hPG

A
  • Placental growth hormone secreted by the placenta responsible for regulating fetal growth
  • Induces maternal insulin resistance
  • No evidence of that maternal GH or fetal GH required for fetal growth
42
Q

Effects of placental CRH

A
  • Stimulates production maternal: ACTH and cortisol
  • Increased cortisol believed to be detrimental to the foetus
  • Increased cortisol can result in increased maternal glucose
43
Q

Why is increased cortisol levels believed to be detrimental to the foetus

A
  • High levels early linked to slower rate of cognitive development post-partum
  • High levels late linked to accelerated cognitive development post-partum
44
Q

Effects of progesterone

A
  • Maintains uterine quiescence by decreasing uterine electrical activity
  • Immune suppressor (HLA)
  • Lobulo-alveolar development in breasts
  • Substrate for fetal adrenal corticoid synthesis eg cortisol
45
Q

Effects of oestrogen

A
  • Growth of the uterus, cervical changes
  • Development of ductal system of breasts
  • Stimulation of prolactin synthesis
  • Stimulation of corticol binding globulin (CBG), sex hormone binding globulin(SHBG), thyroxin binding globulin (TBG)
  • Both maternal and foetal dehydroepiandrosterone(DHEA-S) is converted to oestriol(asomatase)
46
Q

What is most of oestrogen produced as

A
  • 90% as oestriol(to modulating uteroplacental blood flow)

Year 2 - T2 Theme 2 (11 decks)

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