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203 - Theme 2 - Reproductive System, Fetal Development, Pregnancy and Birth > L18 Physiology of Pregnancy > Flashcards

L18 Physiology of Pregnancy Flashcards

1
Q

Volume homeostasis

A

Rapid increase in plasma volume by 40%

  • 2.5L to 3.7L by end of pregnancy
  • 11-13kg weight gain (8-10kg fluid)

Plasma colloid osmotic pressure

  • causes a shift of fluid into extra cellular space
  • increased hydration of connective tissue
  • oedema (lower limbs, hands and face)
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2
Q

Mechanism of increased plasma volume

A

Slight decrease in atrial natriuretic peptide ANP

Decreased thirst threshold (increased fluid intake)

Re-setting osmostat

INCREASED PLASMA VOLUME

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3
Q

What happens to red blood cells during pregnancy?

A

Haemoglobin

  • red cell mass increases by 25% (1.3L to 1.7L)
  • plasma volume increases by 40%
  • 13.3 to 10.9 g/dL at 36 weeks
  • dilutional anaemia
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4
Q

Iron in pregnancy

A

Iron is required for the increased red cell mass

  • fall in ferritin levels
  • increased iron absorption from gut
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5
Q

When do you need to give Fe supplementation?

A

twin pregnancy

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6
Q

What happens to the delivery of blood to the uterus?

A

Uterine artery blood flow increases 3.5 fold from 95 to 342 ml/min

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7
Q

Haemostats in pregnancy

A

Hypercoagulable state
-increase plasma fibrinogen (increased ESR), platelets, factor VIII & 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

White blood cells 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

Increased blood volume during pregnancy has implications on

A

Cardiac output

Peripheral resistance

Blood pressure

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10
Q

Cardiac output =

A

SV x HR

Increased SV required increased heart volume

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11
Q

Heart changes during pregnancy

A

Heart enlarges by 12% (increased venous return)

Innocent systolic murmurs are common (approx 90%)

Diastolic murmurs (approx 20%) - require investigation to rule out other pathologies

  • 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

What happens to peripheral resistance during pregnancy?

A

Peripheral vasodilation (effect of progesterone)

Peripheral resistance decreases by 35%

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13
Q

Effect of pregnancy on BP

A

Decreased peripheral resistance compensated by the increase in cardiac output

results in small change in BP

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14
Q

Effect on respiratory system

A

increased pulmonary blood flow matched by

increase tidal flow

decrease maternal pCO2 and increase 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 & 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

Effect of pregnancy on renal system 1

A

Kidney increases 1cm size during normal pregnancy

GFR and effective renal plasma flow increase 50+%

BUT tubular reabsorption capacity is unchanged
- leads to decrease in glucose reabsorption thus glycosuria is common

17
Q

Effect of pregnancy on renal system 2

A

Plasma levels of creatinine and urea decrease in pregnancy

All the increments are present by the second trimester

Reduction in GFR of 15 % during the third trimester

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

18
Q

Effects on GI

A

Gastro-oesophageal reflux up to 70 %
- due to increase abdominal pressure, reduced pyloric sphincter with back wash of bile secondary to hormonal changes

Slowing of gut motility and constipation (progesterone effect)

19
Q

simple measures to reduce reflux

A

avoidance of fat and alcohol

upright posture and antacids

20
Q

effect on glucose metabolism: 1st trimester

A

increased sensitivity to insulin thus mothers increase glycogen synthesis and fat deposition

21
Q

effect on glucose metabolism: 2nd trimester

A

insulin resistance

cortisol, progesterone, HPL, & 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)

22
Q

Effects on folate: DNA synthesis, repair and regulation

A

Important in rapid cell division (embryos)

deficiency in pregnancy associated with neural tube defects

23
Q

Effects on folate: RBC development

A

macrocytic anaemia

24
Q

daily folate requirement increases from what to what

A

50mg to 400mg

25
Q

plasma folate represents

A

current nutritional status but significant tissue stores e.g. liver - RBS folate is a good biomarker (no change in pregnancy)

26
Q

no need for folate supplementation BUT

A

prevents neural tube defects this routinely given preconception to 3 months

27
Q

effect on thyroid function

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

placenta as what kind of organ

A

endocrine

29
Q

placenta: protein hormones

A

hCG (human chorionic gonadotrophin)

hPL (human placental lactogen)

hPG (human placental gonadotrophin

CRH (corticotropin releasing hormone)

30
Q

placenta: steroid hormones

A

progesterone

oestrogen

31
Q

Human chorionic gonadotrophin (hCG; 1 of 2)

A

First detectable 8-9 days after ovulation & peaks at 8-10 weeks

Beta subunit used as the pregnancy test

Doubles every 48-72 hours

Produced by the trophoblast

Produced in large quantities by hydatidiform molar pregnancy & choriocarcinoma

Usually significantly lower in ectopic pregnancy & risk of miscarriages

32
Q

Human chorionic gonadotrophin (hCG; 2 of 2)

A

Alpha subunit very similar to LH, FSH,TSH

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

Maintains corpus luteum secretion of progesterone & 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

33
Q

Human placental lactogen (hPL)

A

Similar structure to prolactin and growth hormone

The bigger the placenta, the more hPL

Half life ~ 30 min

Not functioning as a stimulator of lactogenesis

Alters maternal carbohydrate and lipid metabolism to provide for foetal requirements
-Mobilizing 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

34
Q

Placental growth hormone (hPG)

A

Placental Growth Hormone secreted by the placenta responsible for regulating fatal growth

Induces maternal insulin resistance

No evidence of that maternal GH or fetal GH required for fetal growth

35
Q

Placental corticotrophin-releasing hormone (CRH)

A

Stimulates production of maternal:

  • adrenocorticotropin hormone (ACTH)
  • cortisol

? Increased cortisol believed to be detrimental to the foetus ?

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

Increased cortisol can result in increased maternal glucose

36
Q

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

37
Q

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 & foetal dehydroepiandrosterone (DHEA-S) is converted to oestriol (aromatase)

90% as oestriol (to modulating uteroplacental blood flow)

203 - Theme 2 - Reproductive System, Fetal Development, Pregnancy and Birth (17 decks)

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