9. Pregnancy Flashcards
Weight gain during pregnancy
average
increase bmr
Maj fat store laid down when ~ how much
How much does ecf increase
where else is the weight gain
The average weight gain is about 12 kilograms and the basal metabolic rate is increased by about 15% at term.
Fat stores are laid down by the mother, primarily in the first half of pregnancy and account for approximately 3 kilograms (not 6 kg).
The extracellular fluid increases by 3 litres (not intracellular).
The other major components of maternal weight gain during pregnancy involve the breasts and uterus.
Change to blood volume
Change esr and CRP
Platelet change
albumin chanbge
At term, the total blood volume (red cell volume + plasma volume) is 48% greater than pre-pregnancy levels.1
The ESR (and CRP) increases during pregnancy as a result of a rise in circulating fibrinogen.2
Whilst platelet turnover increases during pregnancy, an increase in production typically leads to only a small fall in platelet count (<5%).3
Albumin production fails to keep up with the expansion in plasma volume and leads to a reduction in colloid osmotic pressure and the formation of oedema. A typical serum albumin value in the non-pregnant state ranges from 33-41 g/L compared with 24-31 g/L during the third timester of pregnancy.
Cardiac changes in pregnancy
SV
SVR
SBP DBP
HR
CVP & PCWP
Stroke volume increases by 20-30% during pregnancy.
The systemic vascular resistance decreases by about 30% due to hormone-mediated vasodilation.
The systolic and diastolic blood pressures decrease by 10% at 20 weeks gestation.
Heart rate increases by 25% in the middle of the third trimester.
Central venous pressures and pulmonary capillary wedge pressures remain stable.
The physiological changes in a normal pregnancy affect most of the organ systems in the body and are summarised as follows:
- CVS
x5
Resp
x4
Renal x7
- The Cardiovascular System
An increased cardiac output
A 30% increase in stroke volume
A 15% increase in heart rate
Decreased peripheral vascular resistance and lowered diastolic blood pressure
Increased organ blood flow.
The haematological changes are discussed in a separate question.
- The Respiratory System
An increased minute volume due to a 40% increase in tidal volume (small change in respiratory rate)
Decrease in functional residual capacity
A respiratory alkalosis
An increase in CO2 production.
- The Renal System
Increased total body water by up to 8 litres
Increased renal plasma flow
A 50% increase in glomerular filtration rate (not 25%)
A decrease in plasma osmolality (by 10 mosmol/kg) and specific gravity
Decreased plasma sodium, potassium, urea and creatinine concentrations
Sodium and potassium retention
A reduced tubular threshold for glucose.
- The Gastrointestinal System
Decreased lower oesophageal sphincter tone.
Qs/QT in term pregnancy different positions
What is the cause of this
Qs/Qt in a group of pregnant volunteers at term. They found that directly measured Qs/Qt averaged:
- 3% in the left lateral
- 2% in the right lateral
- 9% in the supine
- 8% in the knee-chest
- 8% in the sitting, and
- 0% in the standing positio
This represented a marked increase in venous admixture in comparison with the non-pregnant state.
DOes red cell mass increase
what happens to platelet count
What happens to plasma cholinesterase
change to clott factors
what about bleeing times
The increase in red cell mass is less than the increase in plasma volume, resulting in the physiological anaemia of pregnancy.
The platelet count is normal or slightly reduced due to dilution and there is a 30% reduction in plasma cholinesterase concentration at term.
There are significant increases in concentrations of factors VII, VIII, IX, X and fibrinogen but bleeding, clotting (prothrombin time) and clot retraction time remain unchanged in the healthy pregnant patient.
Oxytocing
side effects
why
dose at LCS
what effects has it
xytocin is a commonly used uterotonic that can cause significant and even fatal hypotension (not hypertension), particularly when given as a bolus. The resulting hypotension can be produced by a decrease in systemic vascular resistance or cardiac output through a decrease in venous return
A slow bolus of 5 IU (not 10) is recommended at lower segment caesarean section.
Oxytocin promotes lactation and has an antidiuretic effect, but it has no effect on the lower oesophageal sphincter pressure
MV - Term
Why
What hormones affect what organ
what is the expected paco2 & bic
Minute ventilation at term is increased by about 50% primarily due to an increased tidal volume with little change or at most a slight increase in respiratory rate. Progesterone, oestradiol and prostaglandins are thought to influence hypothalamic function. This causes a mild compensated respiratory alkalosis.
As a result of this increased alveolar ventilation at term maternal PaCO2 is usually decreased to about 32 mmHg (4.27 kPa). The impact of a maternal alkalosis is lessened by a compensatory decrease in serum bicarbonate from 27 to 21 mmol/L by renal excretion.
Permeability of o2 & co2
how transported
how gluc tported
what ig crosses - how
what about aa
Oxygen and carbon dioxide have a very high permeability and are transferred by flow-limited passive diffusion.
Glucose is transferred by facilitated diffusion and calcium by active carrier-mediated transport (not passive diffusion).
Immunoglobulin IgG crosses by endocytosis and amino acids are actively transported by transporter proteins or a sodium-dependent carrier system.
Haem changes preg
blood vol
plasma
eryhthro
platelts
hct & viscosity
increase in what factors
affect on wbc
fibronlysis
The haematological changes associated with a normal pregnancy are as follows:
30-50% increase in blood volume
30-40% increase in plasma volume
20-30% increase in erythrocytes
lowered platelet count
reduced haematocrit and viscosity, and
increase in coagulation factors I (fibrinogen), VII, VIII, IX, X, and XII thus increasing coagulability (not factors II and V).
A mild leukocytosis can occur in normal pregnancy. Leukocytosis is considered to be evidence of an increased inflammatory response during normal pregnancy and in preeclampsia.
Fibrinolysis was previously thought to be inhibited though research suggests that fibrinolysis is increased
Proteinuria - what % pregnancy
GFR increase how much trimester
Max tubular resporption threhold glucose
Progesterone does what to bladder
urinary freq
Proteinuria is present in 20% of normal pregnancies.
The glomerular filtration rate increases by 50% during the first trimester.
The maximal tubular resorption threshold for glucose is reduced and intermittent glycosuria is common.
Progesterone relaxes the bladder and urinary frequency is common, due to mechanical compression of the bladder by the uterus.
Caommonest cause of anaemia preg
Defin anaemia trimesterally
What other bloods are abnormal in IDA
What further test might establish IDA
What factors lead to IDA in pregnancy
The limited haematological picture of this patient is one of a mild normocytic anaemia and normal platelet count.
The commonest cause of anaemia during pregnancy is iron deficiency. It can occur in 75-95% of patients. Anaemia is defined as a haemoglobin of less than 110 g/L in the first trimester and <105 g/L in the second and third trimesters.
In addition to a low haemoglobin, typically there will be a low mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC). For mild cases of iron or coexisting vitamin B12 and folate deficiency, the MCV may be normal.
Further tests are required to establish iron deficiency. These include a low serum ferritin (<15 µg/L) and less reliable indices such as serum iron and total iron binding capacity.
Iron deficiency in pregnancy results from a number of factors, these are:
Insufficient dietary iron to meet the nutritional needs of the mother and fetus
Multiple pregnancy
Blood loss, and
Reduced iron absorption from the gut.
During pregnancy the plasma volume increases by approximately 50%, but red blood cell (RBC) mass increases by only 30%. This situation results in a dilutional anemia. The RBC mass increases linearly from the first trimester to delivery and the plasma volume plateaus or stabilises or falls slightly near term. Therefore haemoglobin concentrations are lowest between 28 and 34 weeks’ gestation. This patient is 37-weeks pregnant and the effects of haemodilution will have been negated.
A less common anaemia in pregnancy is vitamin B12 and folate deficiency. The normal MCV might preclude the diagnosis.
The platelet count does decrease during pregnancy, particularly in the third trimester. This is termed as “gestational thrombocytopenia”. It is partly due to haemodilution and partly due to increased platelet activation and accelerated clearance. Thrombocytopenia typically occurs in pre-eclampsia and HELLP syndrome. Pre-eclampsia per se is not a primary cause of anaemia.
A typical blood picture of a haemoglobinopathy such as sickle cell disease results in quantitative and qualitative defects, the former resulting in a severe anaemia exacerbated by haemodilution and factors that contribute towards iron deficiency. The cells are typically microcytic.
Affect pregnancy on total resp compiance
why
affect on lung compliance
Affect on FRC - why
What hormone affect respiratory centre - does what
how is that compensated
There is a reduction in total respiratory compliance due to a decrease in chest wall compliance, but lung compliance is not altered.
The functional residual capacity (FRC) is reduced by 20% (not increased), which is mainly due to elevation of the diaphragm.
Progesterone stimulates the respiratory centre producing primarily an increase in tidal volume with a relatively constant respiratory rate, this leads to a respiratory alkalosis which is compensated for by a reduction in plasma bicarbonate level
What does pituitary gland do to production of horomones
what concentrations of circulating hormones increase
what about thyroid
The pituitary gland increases the production of prolactin and adrenocorticotrophin (ACTH) but the production of growth hormone is reduced (not increased).
Plasma concentrations of cortisol, aldosterone, renin and angiotensin rise.
There is an increase in the production thyroid hormone, but an increase in production of thyroid binding globulin means that the free plasma concentration of thyroid hormones (thyroxine) remains unchanged (not increased).
PGA x3 1/tri
PGE 3rd/tri
Oxytocin
produced where
release where
primary role
how does it do this
clin use synthetic oxy
how does it achieve
Is it similar to adh
how much so
is this a problem
Oxytocin is synthesised in the paraventricular nucleus of the hypothalamus and is then transported in secretory granules along axons to the posterior pituitary gland, from which it is released.
The primary role of oxytocin is to eject milk from the lactating mammary gland in response to suckling. It achieves this by causing contraction of the myoepithelial cells that surround the alveoli of the mammary gland.
The principal clinical uses of synthetic oxytocin are to induce labour at term and to induce sustained uterine contraction which is required for postpartum or post-termination haemostasis.
By Reducing the threshold for depolarisation of uterine smooth muscle, oxytocin exerts a contracting effect on the gravid uterus. The sensitivity of the uterus to oxytocin increases as the pregnancy progresses.
Oxytocin has only 0.5-1% of the antidiuretic activity of ADH (antidiuretic hormone) when administered in high doses, introducing the possibility of water intoxication.
