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Reproductive System > Physiology in Pregnancy > Flashcards

Physiology in Pregnancy Flashcards

1
Q

What are some mechanical changes during pregnancy?

A
  • Centre of gravity no longer over feet
    • Due to increased blood volume and enlarged foetus
    • Needs to lean backwards to counter which causes back pain
  • Increased pliability and extensibility of connective tissue
    • Due to relaxin, a hormone produced during pregnancy, and increased levels of oestrogen and progesterone
    • Causes ligamentous joints to become less stable, symphysis pubis and sacroiliac joints are particularly affected to allow for birth of baby, normal pubic symphyseal gap increases from 4-5mm by another 3mm
      • Can cause pubic symphysis dysfunction
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2
Q

Why is the centre of gravity no longer over the feet during pregnancy?

A
  • Due to increased blood volume and enlarged foetus
  • Needs to lean backwards to counter which causes back pain
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3
Q

What causes increased pliability and extensibility of connective tissue during pregnancy?

A
  • Due to relaxin, a hormone produced during pregnancy, and increased levels of oestrogen and progesterone
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4
Q

What is a complication of increased pliability and extensibility of connective tissue during pregnancy?

A
  • Causes ligamentous joints to become less stable, symphysis pubis and sacroiliac joints are particularly affected to allow for birth of baby, normal pubic symphyseal gap increases from 4-5mm by another 3mm
    • Can cause pubic symphysis dysfunction
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5
Q

What metabolic changes occur during pregnancy?

A
  • Basal metabolic rate increases
    • Ensure adequate nutrition for foetal growth
  • Insulin insensitivity
    • Human placental lactogen produced by placental acts against maternal insulin
      • Can cause gestational diabetes
  • Increased storage of lipids in maternal tissues
    • Fatty acids vital for foetal organogenesis
  • Weight gain of 10-14kg throughout pregnancy considered normal
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6
Q

Why does insulin insensitivity occur during pregnancy?

A
  • Human placental lactogen produced by placental acts against maternal insulin
    • Can cause gestational diabetes
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7
Q

A weight gain of what during pregnancy is considered normal?

A

10-14kg

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8
Q

Fatigue during pregnancy is likely due to what?

A

Likely due to hormonal changes:

  • Worst in first trimester, gets better in second then returns towards end of pregnancy
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9
Q

Why does heartburn/reflux occur during pregnancy?

A
  • Food moves more slowly into stomach and delayed emptying
  • Hormones cause relaxation of lower oesophageal sphincter so contents more likely to reflux from stomach to oesophagus
  • Mechanical pressure from enlarging uterus
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10
Q

What is a complication of heartburn/reflux during pregnancy?

A

This is why general anaesthetic is much higher risk in pregnancy, greater risk of aspiration

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11
Q

Why does oedema occur during pregnancy?

A
  • Sodium and water retention and decreased ability to excrete sodium and water load
  • Increased blood volume and decreased venous return due to compression of IVC from the gravid uterus
  • 80% experience this
  • Can be important sign of pre-eclampsia
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12
Q

What changes to the breasts occur during pregnancy?

A
  • Increase in size and vascularity
  • Become warm, tense and tender
  • Increased pigmentation of the areola and nipple, and secondary areola appears
  • Montgomery tubercles appear on the areola
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13
Q

Why does immunosuppresion occur during pregnancy?

A

Allows for foetal tolerance:

  • Increases maternal susceptibility to infection
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14
Q

What is a complication of immunosuppresion during pregnancy?

A
  • Increases maternal susceptibility to infection
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15
Q

What changes occur in the thyroid during pregnancy?

A
  • Liver produces more thyroid binding globulin (TBG) but total level of thyroxine (T4) and tri-iodothyronine (T3) also increases so free T3 and T4 remains the same
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16
Q

During pregnancy, do iodine requirements increase or decrease?

A
  • Pregnancy associated with relative iodine deficiency
    • Maternal iodine requirements increase because iodine activity is linked to fetoplacental unit and urinary iodine excretion is doubled due to increased GFR and decreased renal tubular reabsorption
    • Causing thyroid gland to work harder to increase its iodine uptake and may hypertrophy
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17
Q

Why do iodine requirements increase during pregnancy?

A
  • Maternal iodine requirements increase because iodine activity is linked to fetoplacental unit and urinary iodine excretion is doubled due to increased GFR and decreased renal tubular reabsorption
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18
Q

Why can hypermesis gravidarum occur during pregnancy?

A
  • Hyperemesis gravidarum can be associated with biochemical hyperthyroidism (increased levels of T4 and suppressed TSH)
    • Because of the beta subunit of BHCG (a pregnancy hormone) is structurally similar to TSH
    • Beta blockers used for symptoms control of tachycardia caused by high levels of T4
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19
Q

Why might thyrotoxicosis occur in pregnancy?

A
  • 1 in 500 pregnancies
  • Most often due to Graves
  • The antibodies that cause Graves disease (TSH receptor antibodies) can cross the placenta and cause fetal and/or neonatal hyperthyroidism
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20
Q

How may hypothyroidism affect pregnancy?

A
  • Affects approximately 1% of pregnancies
  • The foetus is dependent on maternal thyroid function until fetal thyroid function begins at around 12 weeks gestation
  • It is important to ensure good thyroid replacement prior to pregnancy
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21
Q

What are some physiological changes during pregnancy (vague categories)?

A

Mechanical changes

Metabolic changes

Fatigue

Heartburn/reflux

Oedema

Breast changes

Thyroid changes

Changes to various systems (CVS, respiratory, renal, haematological)

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22
Q

Why does the heart need to work harder during pregnancy?

A
  • Weight gain
  • Growing foetus
  • Increased oxygen requirements of uterus and breasts
  • Pump blood through foetal circulation
23
Q

What is the leading cause of maternal death in the UK?

A

Cardiac disease

24
Q

What changes occur in the cardiac system during pregnancy?

(5)

A
  • Circulatory blood volume increased by 50-70%
    • Causes the left ventricular end diastolic volume to increase, can be seen as early as 10 weeks on ECHO
  • Red cell mas increased by 40% causing relative haemodilution
    • Cause of physiological anaemia of pregnancy
  • Systemic vascular resistance falls
    • Due to increased circulating vasodilators and diversion of blood into low pressure uteroplacental unit
  • Increase in blood flow to some organs
    • Such as kidneys, 60-80% increase
    • Warm, red hands and feet caused by this
    • Nasal mucosa, increasing nose bleeds
  • Increased cardiac output, by 30-50%
    • Due to increased stroke volume and heart rate (10-20 beats per minute more)
25
Q

What are consequences of circulatory blood volume increasing during pregnancy?

A
  • Causes the left ventricular end diastolic volume to increase, can be seen as early as 10 weeks on ECHO
26
Q

What is a complication of red cell mass increasing during pregnancy?

A
  • Red cell mas increased by 40% causing relative haemodilution
    • Cause of physiological anaemia of pregnancy
27
Q

How does systemic vascular resistance change during pregnancy?

A
  • Systemic vascular resistance falls
    • Due to increased circulating vasodilators and diversion of blood into low pressure uteroplacental unit
28
Q

What formula describes systemic vascular resistance?

A
29
Q

What formula describes cardiac output?

A
30
Q

How does preganancy affect HR?

A
  • By term, the heart rate of a pregnant person is usually approximately 10-20 beats higher
  • Whilst a sinus tachycardia is not uncommon other pathologies causing tachycardia such as hypovolaemia, pulmonary embolus, sepsis should be considered depending on the clinical context
31
Q

How dooes pregnancy affect oxygen consumption?

A
  • Can increase by 20-30% by term
  • The myocardium has to work harder because of the marathon challenge of pregnancy and therefore requires more oxygen
  • For people with coronary artery disease (older/obese/diabetic/smoker) there is a risk of pregnancy triggering ischaemic heart disease and myocardial infarction
32
Q

Why should pregnant woman not lie supine?

A
  • Pregnant woman lying supine lose 25% of cardiac output due to compression on vena cava by uterus – NEVER LIE PREGNANT WOMAN FLAT
33
Q

What is the advice during an event of maternal cardiac arrest?

A
  • Patient MUST be resuscitated on left lateral tilt or with uterus manually displaced
  • Will not be able to resuscitate on the flat due to reduction in cardiac output this causes
34
Q

When is intrapartum?

A

Time between onset of labour and delivery of placenta

35
Q

What are some intrapartum CVS changes?

A
  • Autotransfusion of contractions
    • With every contraction 500mls of blood is dumped into circulation
  • Pain
    • Increases circulating catecholamines and increases heart rate, blood pressure and cardiac output
36
Q

What is the effect of labour on cardiac output?

A
  • Autotransfusion of contractions and pain lead to increased CO
  • After delivery, CO is increased further due to loss of uteroplacental unit and relief of pressure on IVC
37
Q

What is postpartum?

A

First 6 weeks after chilldbirth

38
Q

What are the postpartum cardiovascular changes?

A
  • Most changes return to normal by 3mth post delivery
  • 3 days post delivery the blood volume will have decreased by 10%
  • The blood pressure (BP) initially falls then increases again by 3-7 days after birth
  • The BP returns to prepregnancy levels by 6 weeks
  • The systemic vascular resistance begins to increase again over the first two weeks and the heart rate falls to prepregnancy levels over a similar time frame
39
Q

What are some respiratory changes during pregnancy?

A
  • Tidal volume increased, 40-50% increase in minute ventilation
  • Respiratory rate increases
    • This hyperventilation lowers PCO2 and healthy person in state of compensated respiratory alkalosis
  • Enlarged uterus pushes up diaphragm by 4cm and increases diameter of lower thorax by 2cm by splaying the lower ribs
  • Functional residual capacity reduces by 20-30%
    • Further reduced by supine position
40
Q

What are complications of respiratory rate increasing during pregnancy?

A
  • This hyperventilation lowers PCO2 and healthy person in state of compensated respiratory alkalosis
41
Q

What are some haematological changes during pregnancy?

A
  • Decreased haemoglobin (Hg)
    • At 28 weeks 105g/L considered normal (when non-pregnant is 120-160g/L)
    • Due to circulating blood volume increasing by 50-70% but red blood cell mass only by 40%
  • Plasma volume increases proportional to birth weight
    • Relative decrease in platelet count, but generally remains within normal limits
  • 2-3x increase in iron requirements for use of foetus as well as increasing red cell mass
    • Means iron deficiency anaemia is most common haematological abnormality during pregnancy
      • More common in twin pregnancy
  • 10-20x increase in folate requirements
    • Folate serum levels lower but liver levels maintained
  • White cell count (WCC) and neutrophil count is increased
    • WCC of up to 16x10g/L normal
  • Hypercoagulable state, the factors which promote clotting increases, factors which decrease clotting decrease
    • Clotting factors VII, IX and X increase as does fibrinogen
    • Protein S and C and anti-thrombin 3 levels decrease
    • Fibrinolytic activity decreases
    • Complication is pulmonary embolism is one of main causes of maternal mortality
      • Pregnancy increases risk of thromboembolism by 6x
    • Changes occur from very early in pregnancy to 6 weeks after delivery
42
Q

What is considered to be normal haemoglobin level at 28 weeks?

A
  • At 28 weeks 105g/L considered normal (when non-pregnant is 120-160g/L)
43
Q

Why does haemoglobin decrease during pregnancy?

A
  • Due to circulating blood volume increasing by 50-70% but red blood cell mass only by 40%
44
Q

What is a complication of increases iron requirements during pregnancy?

A
  • 2-3x increase in iron requirements for use of foetus as well as increasing red cell mass
    • Means iron deficiency anaemia is most common haematological abnormality during pregnancy
      • More common in twin pregnancy
45
Q

By what scale do folate requirements increase during pregnancy?

A

10-20x

46
Q

How does WCC and neutrophil count change in pregnancy?

A
  • White cell count (WCC) and neutrophil count is increased
    • WCC of up to 16x10^9g/L normal
      • (otherwise 11x10^9g/L)
47
Q

What causes the hypercoagulable state of pregnancy?

A
  • Clotting factors VII, IX and X increase as does fibrinogen
  • Protein S and C and anti-thrombin 3 levels decrease
  • Fibrinolytic activity decreases
48
Q

What is a complication of the hypercoagulable state of pregnancy?

A
  • Complication is pulmonary embolism is one of main causes of maternal mortality
    • Pregnancy increases risk of thromboembolism by 6x
  • Changes occur from very early in pregnancy to 6 weeks after delivery
49
Q

What changes happen to the renal system during pregnancy?

A
  • Dilatation of the urinary collecting system due to relaxation of smooth muscle of ureter caused by progesterone and mechanical compression of uterus
  • Physiological hydronephrosis
    • ​More pronounced on the right
  • Increase in renal plasma flow by 60-80%
    • Due to increase in circulating blood volume and reduction in systemic vascular resistance
    • (50% 3rd trimester)
  • GFR and creatinine clearance increases by 50%
  • Kidneys excrete more protein but retain more sodium and water
  • Secretion of vitamin D, renin and erythropoietin increases
50
Q

What causes dilation of the urinary collecting system during pregnancy?

A
  • Dilatation of the urinary collecting system due to relaxation of smooth muscle of ureter caused by progesterone and mechanical compression of uterus
51
Q

How does renal plasma flow change during pregnancy?

A
  • Increase in renal plasma flow by 60-80%
    • Due to increase in circulating blood volume and reduction in systemic vascular resistance
52
Q

How does GFR change during pregnancy?

A
  • GFR and creatinine clearance increases by 50%
53
Q

What are some common conditions of the renal system during pregnancy?

A
  • Microscopic haematuria
    • If other conditions excluded, likely due to bleeding from small vessels in the dilated renal function
  • Glycouria
  • Urinary tract infection
  • Any underlying kidney disease is likely to worsen during pregnancy because of the additional work being done by the renal system

Reproductive System (31 decks)

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