Physiological Changes In Pregnancy

Front 1

When do most women begin to report symptoms of pregnancy?

Back 1

By the end of the sixth week after the last menstrual period.

Front 2

How is increased availability of precursors for hormone production and foetal-placental metabolism achieved?

Back 2

Increased availability of metabolic substrates and hormones is achieved by increases in dietary intake, as well as endocrine changes that increase the availability of substrates like glucose.

Front 3

How is transport capacity improved?

Back 3

Increased cardiac output

Front 4

How is the maternal foetal-exchange managed throughout gestation?

Back 4

The placenta regulates maternal-foetal exchange by 10-12 weeks gestation, but transfer occurs though other mechanisms before this.

Front 5

How are additional waste products disposed of?

Back 5

Disposal of heat - peripheral vasodilatation.
Disposal of CO2 - ventilation.
Disposal of metabolic byproducts - renal filtration.

Front 6

Why does the maternal blood volume expand during pregnancy?

Back 6

To allow adequate perfusion of vital organs, including placenta and foetus.
To anticipate blood loss associated with delivery.

Front 7

In what compartment does the maternal blood volume increase?

Back 7

It increases in both the intracellular and extracellular, but is more marked in the ECF, especially the plasma volume.

Front 8

How much does total body water increase during pregnancy?

Back 8

6.5 - 8.5kg.

Front 9

Broadly speaking what are the consequences of fluid retention during pregnancy?

Back 9

The concentrations of certain substances in circulation decrease (e.g. Hb, HCT, albumin), whereas there is a marked increase in haemodynamics (CO and GFR).

Front 10

What is the mechanism behind fluid retention in pregnancy?

Back 10

Changes in RAAS system result in active sodium reabsorption in the renal tubules. Sodium is sequestered within the foetal tissues.

Front 11

What factors contribute to fluid retention?

Back 11

1. sodium retention
2. resetting of osmostat (plasma osmolatlity decreases by 10mOsmol/kg)
3. decreased thirst threshold
4. decreased plasma oncotic pressure (due to decreased albumin concentration)

Front 12

What causes the physiological anaemia of pregnancy?

Back 12

1. Increased plasma volume
2. Increased erythrocyte mass
3. Transfer of iron stores to the foetus

Front 13

What is the mean haemoglobin concentration for a pregnant woman?

Back 13

The mean Hb concentration falls from 13.3g/dL in a non-pregnant state to 10.9g/dL at the 36th week of pregnancy.

Front 14

What is a normal pregnancy haematocrit?

Back 14

32-34%, which is lower than non-pregnant values.

Front 15

Do pregnant women require increased amounts of iron?

Back 15

Yes. Even though there is increased absorption of dietary iron from the gut, women who do not take supplementary iron during pregnancy show a reduction in bone marrow iron and are still low six months after delivery.

Front 16

What happens to renal clearance of folic acid during normal pregnancy?

Back 16

Increases.

Front 17

What happens to plasma folate concentrations in normal pregnancy?

Back 17

They fall. However, red cell folate concentrations do not decrease to the same extent.

Front 18

What happens to the platelet count during pregnancy?

Back 18

The maternal platelet count usually remains stable, though may slightly decrease due to increased platelet aggregation, and then increase in the first week post-partum, putting pregnant women at risk of VTE.

Front 19

What happens to the procoagulant factors during pregnancy?

Back 19

They increase. Almost all factors increase, indlucing VII, VII, IX, X, XII and fibrinogen, and vWF (which is a crrier for factor VIII)

Front 20

What happens to plasma D-dimer concentration during pregnancy and what impact does this have on VTE?

Back 20

Maternal plasma D-dimer concentration increase from conception until delivery, and therefore limits the use of D-dimer testing to rule out VTE.

Front 21

Why and how is the fibrinolytic system activated during pregnancy?

Back 21

It is activated to counterbalance the increase in coagulation factors. There is increase in D-dimers, fibrin degradation products, plasminogen and activators of plasminogen.

Front 22

Why is hypercoaguability important for delivery?

Back 22

At term, 500 mL of blood flows through the placental bed each minute. Without effective rapid haemostasis, women would die from blood loss.

Front 23

How is haemostasis achieved at delivery?

Back 23

1. Myometrial contractions first compress the blood vessels supplying the placental bed.
2. Fibrin depostion over the placental site (to form clot).

Front 24

What happens to plasma protein concentrations during pregnancy?

Back 24

They are decreased, especially albumin.

Front 25

What are the effects of the decreased plasma protein concentration during pregnancy?

Back 25

The plasma oncotic pressure is reduced.
The peak plasma concentration of drugs which are protein bound is reduced. Some drugs may be less effective.

Front 26

What happens to the concentration of serum creatinine, uric acid are urea concentrations?

Back 26

They are all reduced during normal pregnancy, although the renal handling of uric acid changes in late gestation, resulting in increased reabsorption.

Front 27

How are LFTs affected during pregnancy?

Back 27

ALP levels increase due to production of placental ALP. ALT and AST are often lower.

Front 28

What is the reference value for haemoglobin in normal pregnancy?

Back 28

11.0 g/dL

Front 29

What is the reference range for HCT in normal pregnancy?

Back 29

32-24%

Front 30

What is the reference value for albumin in normal pregnancy?

Back 30

23 - 28 g/L

Front 31

What problems related to brain function do women report during pregnancy?

Back 31

Attention, concentration and memory deficits during pregnancy and the early post-partum period.

Front 32

Do pregnant women require the same amount of local anaesthetic in the epidural/intrathecal space as non-pregnant women?

Back 32

No, they require less.

Front 33

Why do pregnant women have an increased tolerance for pain?

Back 33

Due to increased serum levels of beta-endorphins and activated spinal cord kappa-opiate receptors.

Front 34

How does perception of odours change during pregnancy?

Back 34

Aversion to some odours is common in early gestation. Olfactory sensitivity than decreases during the third trimester.

Front 35

What happens to the corneal sensitivity in most pregnant women?

Back 35

Decreases while preganant and the returns to normal by 8 weeks post partum.

Front 36

What can lead to an increase in corneal thickness in the pregnant woman?

Back 36

Oedema
Decreaed tear production

Front 37

Why may pregnant women be intolerant of contacts?

Back 37

Because of the changes in cornea and tear film.

Front 38

What can cause a transient loss of accommodation during pregnancy?

Back 38

The curvature of the crystalline lens can increase causing a myopic shift in refraction and transient loss of accommodation.

Front 39

Why are pregnant women prone to nose bleeds?

Back 39

The vascularity of the respiratory tract mucosa increases and the nasal mucosa can become oedamatous and brone to bleedings.

Front 40

When does ventilation began to increase significantly?

Back 40

At around 8 weeks of gestation, most likely in response to progesterone-related sensitisation of the respiratory centres to carbon dioxide, and also the increased metabolic rate.

Front 41

What is the result of the enlarging uterus elevating the diaphragm?

Back 41

Decreased residual volume and decreased functional residual capacity. FRC is further decreased when supine.

Front 42

What is the effect of relaxin upon the rib cage?

Back 42

It allows the ligaementous attachments of the ribcage to relax, increasing the subcostal angle and changing thoracic anatomy.

Front 43

What is the result of the increased 2,3-DPG concentration in maternal erythrocytes?

Back 43

2,3-DPG preferentially binds to deoxygenated haemoglobin and causes the release of oxygen from red cells, increasing the availability of oxygen to the tissues.

Front 44

How is foetal haemoglobin different from adult haemoglobin and why is this important?

Back 44

Foetal haemoglobin has two beta chains while adult haemoglobin has two gamma chains. Oxygen binds preferentially to beta chains, favouring oxygen transport to the foetus.

Front 45

What happens to blood gas and acid-base levels during pregnancy?

Back 45

Decreased carbondioxide, increased oxygen, slightly altered pH, increased bicarbonate excretion, increased oxygen availability to tissue and placenta.

Front 46

How does pregnancy mimic cardiac disease?

Back 46

Breathlessness: due to elevation of the diaphragm, adjustments of lung volume and increased minute ventilation.
Peripheral oedema: due to increase in total body sodium and water and venous compression by uterus.
Syncope: due to venous compression by uterus impeding blood return.
Palpitations due to sinus tachycardia.

Front 47

Does the heart rate increase or decrease during pregnancy?

Back 47

Increases by 10 - 20%.

Front 48

Does the stroke volume increase or decrease during pregnancy?

Back 48

Increases by 10%.
Elevated at the onset of labour to 7.0 L/ min, increases by 30% in the final stages.
Each uterine contraction squeezes 300 - 500 mL of blood into the maternal circulation.
The CO remains elevated for the first two days post-partum and then falls rapidly for two weeks after delivery.

Front 49

Does the CO increase or decrease during pregnancy?

Back 49

Increases by 30 - 50%.

Front 50

What happens to the mean arterial pressure during pregnancy?

Back 50

Decreases by 10%.

Front 51

What happens to the pulse pressure during pregnancy?

Back 51

It decreases.

Front 52

What happens to peripheral resistance during pregnancy?

Back 52

It decreases by 35%.

Front 53

What ausculatory changes can be heard in pregnancy?

Back 53

Loud first heart sound, sometimes split.
Third heart sound sometimes heard at 20 weeks.
Ejection systolic murmur heard in 96% of normal pregnant women.

Front 54

What are the GIT changes in pregnancy, in terms of oral, liver, gut?

Back 54

Oral: pregnancy gingivitis (erythema, oedema, hyperplasia, increased bleeding); increased tooth mobility.
Gut: reflux oesophagitis due to LOS relaxation caused by elevated progesterone levels; constipation delayed gastric emptying and increased stomach volume; increased risk of aspiration of gastric contents when anaethetised after 16 weeks.
Liver: hyperoestrogenic state can cause telangiectasia and palmar erythema; raised ALP in third trimester; increased production of fibrinogen and clotting factors; hypercholesterolaemia.

Front 55

What are the renal changes in pregnancy?

Back 55

Increase in kidney size.
Dilated renal pelvis and ureters.
Increased blood flow to kidneys.
Increased GFR.
Increased renal plasma flow.
Increased clearance of most substances.
Decreased plasma creatinine, urea, urate.
Glycosuria is normal.

Front 56

Is glycosuria normal or abnormal during pregnancy?

Back 56

It is very common during pregnancy and does not relate reliably to disorders of carbohydrate metabolism.

Front 57

What happens to the uterus during pregnancy?

Back 57

Increased blood flow (700ml/min at term).
Increased weight (50-60g before pregnancy, 1kg by term).
Hypertrophy and later stretching of the uterine arteries.
Development of intercellular gap junctions between myometrial cells.

Front 58

What is the effect of oestrogen on the uterus?

Back 58

Mediates the adaptation of the uterine smooth muscle to pregnancy. Induces hypertrophy and hyperplasia.

Front 59

What is the effect of progesterone on the uterus?

Back 59

Induces hypertrophy and hyperplasia.
Helps maintain low myogenic tone in the uterine vessels.

Front 60

What are Braxton-Hicks contractions?

Back 60

Painless contractions that are noticed in the second half of pregnancy. They are due to the maturation of the gap junctions between myometrial cells.

Front 61

What colour is the cervix during pregnancy?

Back 61

It looks bluer due to increased vascularity.

Front 62

How does the cervix constituency change during pregnancy?

Back 62

Swollen.
Softer.

Front 63

What is the ectropion and what causes it during pregnancy?

Back 63

The growth of the columnar epithelium of the cervical canal. This becomes visible on the ectocervix and is called the ectropion, which is prone to contact bleeding.
Due to the effect of oestradiol.

Front 64

What helps to soften the cervix during late gestation?

Back 64

Prostaglandins induce a remodelling of the cervical collagen.
Collagenase from leukocytes also softens cervix.

Front 65

What happens to the vaginal epithelium under the influence of oestrogen during pregnancy?

Back 65

It becomes more vascular and there is increased desquamation causing increased vaginal discharge.

Front 66

What is the effect of oestrogen on the breasts during pregnancy?

Back 66

Increases the number of glandular ducts.

Front 67

What is the effect of progesterone and human placental lactogen (hPL) on the breasts during pregnancy?

Back 67

Increase the number of gland alveoli.

Front 68

What is the role of prolactin during pregnancy?

Back 68

Stimulates milk secretion and during pregnancy prepares the alveoli for milk production.

Front 69

Why doesn't the increased amounts of prolactin during pregnancy cause lactation?

Back 69

Becuase it is antagonised at an alveolar receptor level by oestrogen. The rapid fall in oestrogen after delivery removes the inhibition and allows lactation to begin.

Front 70

What is the effect of suckling?

Back 70

Suckling stimulates the anterior and posterior piruitary to release prolactin and oxytocin, respectively.

Front 71

What is the role of oxytocin?

Back 71

Oxytocin causes contraction of the myoepithelial cells surrounding the glandular ducts, squeezing milk towards the nipple.
Also facilitates maternal-child bonding.

Front 72

Why is there a fall in TSH and a rise in free T4 during the first trimester of pregnancy?

Back 72

This is because hCG has subunit homology with TSH, therefore supressing maternal TSH production during the first trimester when hCG levels are highest.
With advancing gestation, the free T4 concentration starts to fall...

Front 73

How much weight can a women with pre-pregnancy BMI of <20 be expected to gain to have a healthy baby?

Back 73

12.5 - 18kg.

Front 74

How much weight can a women with pre-pregnancy BMI of 20 - 26 be expected to gain to have a healthy baby?

Back 74

11.5 - 16kg.

Front 75

What are the changes in carbohydrate metabolism during pregnancy?

Back 75

First half: fasting plasma glucose reduced with no change in insulin levels.
Second half: increased in glucose values despite significant increases in plasma insulin concentrations. Suggests insulin resistance.
May allow shunting of nutrients to the foetus?

Front 76

Why is it bad to be vitamin D deficient during pregnancy?

Back 76

Foetal demand for calcium is substantial to ensure skeletal development.
Vitamin D assists in gut calcium absorption.

Front 77

What are the skin changes during pregnancy?

Back 77

Hyperpigmentation.
Increased sebaceous gland activity.
Striae gravidarum.
Hirsutism.