Physiology of pregnancy Flashcards
Mechanical changes in pregnancy
pregnant person needs to lean backward and the curves of the spine change along its whole length. This is why pregnant people are more prone to back pain during (and after) pregnancy.
Hormone produced in pregnancy?
- what effect does this have on
relaxin
- increased pliability and extensibility of connective tissue. Ligamentous joints become less stable.
What joints are particularly affected In pregnancy?
symphysis pubis and sacroiliac joints
the normal pubic symphyseal gap increases by?
4-5mm increase on average by another 3mm. (*symphysis pubis dysfunction).
When does joint loosening occur
load on hip joints at term?
10 weeks and will return to normal 4-12 weeks post partum.
By term there is an increased load on the hip joints of 2.8 times the normal value when standing.
what acts against maternal insulin
Human placental lactogen
what are Fatty acids vital for
fetal organogenesis.
normal female weight gain?
10-14 kg
regarding eating food through pregnancy- what happens?
- what do hormones cause relaxation of? likely to cause?
food moves more slowly into the stomach and there is delayed emptying
- lower oesophageal sphincter - more likely for contents to reflux into oesophagus
The mechanical pressure from an enlarging uterus makes makes what worse as does delayed gastric emptying?
mechanical pressure from an enlarging uterus
what % of women will develop oedema?
80%
why do women develop oedema in pregnancy?
physiological sodium and water retention and a decreased ability to excrete a sodium and water load
increased BV in pregnancy leads to.. why is this?
decreased venous return due to compression of the inferior vena cava from the gravid uterus also contributes to peripheral oedema
oedema can be an important sign of
pre eclampsia
breast changes in pregnancy include?
pigmentation of the areola and nipple and a secondary areola appears
- Montgomery tubercles appear on the areola. Colostrum like fluid can be expressed from the end of the 3rd month.
what does the liver produce more of in pregnancy?
do t3 and t4 change?
thyroid binding globulin (TBG) but the total level of thyroxine (T4) and tri iodothyronine (T3) also increase so FREE T3 and FREE T4 (active) levels remain the same.
what is pregnancy associated with?
a relative iodine deficiency
why do maternal iodine requirements increase in pregnancy?
- urinary exception and GFR?
- why does the thyroid gland work harder?
iodine is actively transported to the fetoplacental unit and urinary iodine excretion is doubled because of an increased glomerular filtration rate and decreased renal tubular reabsorption. The thyroid gland therefore works harder to increase its iodine uptake and may hyperthrophy to ensure adequate levels of iodine trapped.
What can be associated with a biochemical hyperthyroidism (increased levels of T4 and suppressed TSH?
- why is this?
Hyperemesis gravidarum
- because the beta sub unit of BHCG (a pregnancy hormone) is structurally very similar to TSH.
How is Hyperemesis gravidarum treated?
betablockers such as propanolol can be used for symptom control of tachycardia caused by the high levels of T4. This biochemical hyperthyroidism will resolve with the hyperemesis.
what is overactive thyroid caused?
Thyrotoxicosis
Thyrotoxicosis is often due to underlying?
Grave’s disease
What can the antibodies that cause Graves disease do?
what are these antibodies called?
TSH receptor antibodies
- can cross the placenta and cause fetal and/or neonatal hyperthyroidism
what is the foetus dependent on?
maternal thyroid functio
when does fetal thyroid development begin?
12 weeks gestation.
there Is a general state of immunosuppression in pregnancy - why is this?
- what does this do?
to allow for fetal tolerance
- increases the maternal susceptibility to infection
What conditions can improve during pregnancy?
Crohns disease, rheumatoid arthritis
the heart has to work harder due to? (4)
- what does it have too pump blood through?
- of the growing fetus, the weight gain associated with pregnancy and the increased oxygen requirements of the uterus and breasts
previous or undiagnosed cardiac problems may show in pregnancy.. what my happen?
- may lead to maternal and fetal death
-
What is the leading indirect cause of maternal death in the UK?
cardiac disease
circulating blood volume in pregnancy increases by?
relative haemodilution by red cell mass %?
50-70%
- red cell mass also increases
- 40%
what causes the physiological anaemia of pregnancy?
red cell mass also increases by 40% - haemodilution
the increase in circulating BV causes what to increase?
- when will this be seen during gestation
the left ventricular end diastolic volume is increased and can be seen as early as 10 weeks on an echocardiogram (ECHO)
the increased BV in pregnancy can cause problems for those with? (3)
dilated cardiomyopathy or lesions such as mitral stenosis or pulmonary hypertension.
The resistance of all the peripheral vasculature in the systemic circulation (systemic vascular resistance) falls and is at its lowest at between?
20-32 weeks.
(Systemic vascular resistance) equation?
SVR = Mean arterial pressure (MAP) – mean venous pressure (MVP)
divided by
Cardiac output (CO)who does the SVR drop?
because of increased circulating vasodilators and the diversion of blood into the low pressure uteroplacental unit.
blood flow to kidneys increases by?
60-80%
why is cardiac output increased in pregnancy?
the stroke volume – the amount of blood pumped out by the ventricle with each beat - is increased. The heart rate also increases.
how do you calculate cardiac output?
stroke volume x heart rate
cardiac output increases by?
- who is at risk
30-50% by the end of the second trimester
- aortic stenosis - those who can’t increase CO
By term, the heart rate of a pregnant person is usually ?
10-20 beats higher than their non-pregnant value
what heart rhythm is not uncommon in pregnancy?
- what conditions may cause this heart rhythm? (4)
sinus tachycardia
- hypovolaemia, pulmonary embolus, sepsis should be considered depending on the clinical context.
During pregnancy oxygen consumption can increase by ?
- what muscle is working harder
20-30% by term
- myocardium
for those who smoke older/obese/diabetic the risk of developing what condition during pregnancy is…?
those with CAD
- ischaemic heart disease and myocardial infarction
why may a pregnant patient faint?
vena caval compression by the pregnant uterus, any pregnant patient lying supine will lose 25% of their cardiac output
what to do in the event of a maternal collapse/cardiac arrest ??
MUST be resuscitated on a left lateral tilt or with the uterus manually displaced. YOU WILL NOT BE ABLE TO RESUSCITATE ANY PERSON WITH A GRAVID UTERUS WHO IS LYING FLAT BECAUSE OF THE REDUCTION IN CARDIAC OUTPUT THIS CAUSES. This is one of the reasons a perimortem CS/emptying of uterus is part of the pregnancy ALS algorithm.
how much blood is added to circulation with each contraction?
500 mls
why does pain increase Intrapartum?
increases circulating catecholamines and increases the heart rate, blood pressure and cardiac output (CO =SVxHR)
how does CO vary during labour?
- why does it vary?
during - increase of 10%
after - 80% above already increased value
- lack of uteroplacental unit to be supplied but also because of the immediate relief of inferior vena caval compression
BP levels before and after birth
The blood pressure (BP) initially falls then increases again by 3-7 days after birth. The BP returns to prepregnancy levels by 6 weeks
days after post delivery
does BV decrease?
3
what % increase in minute ventilation
RR can also be confused for?
40-50%
- dyspnea
because of relative hyperventilation, PCO2 levels are lower in pregnancy and the pregnant healthy person is in a state of ?
compensated respiratory alkalosis
how does the enlarging uterus affect the diaphragm ?
by as much as 4cm and increases the diameter of the lower thorax by 2cm by splaying the lower ribs.
what reduces by 20-30% in Resp changes?
Functional residual capacity
asthma may improve in pregnancy due to?
the bronchodilator effect of progesterone.
at 28 weeks- what is considered a normal Hg?
105 g/L or above is considered normal
- physiological anaemia
non pregnant reference range of Hg?
120-160g
what results due to the increase of plasma volume?
relative decrease in platelet count
fold increase in iron for the fetus?
a 2-3 fold increase
most common haematological abnormality of pregnancy?
Fe deficiency anaemi
Going in to pregnancy with depleted Fe stores is common and may be due to? (3)
menorrhagia, inadequate diet, previous recent pregnancies
Fe deficiency in pregnancy is also asoociated with?
intrauterine growth restriction
folate increase is?
10-20 fold
- second most common cause of pregnancy anaemia
WCC - normal value?
16x109/L is normal in pregnancy
what clotting factors increase in pregnancy?
factors VII, IX and X increase as does fibrinogen
What clotting factors decrease?
- what activity decreases?
Protein S and C and anti thrombin 3 levels decrease.
- Fibrinolytic activity decreases.
why is t he risk of deep venous thrombosis in pregnancy increased?
- the main causes of direct maternal mortality in the UK is?
venodilation and reduced venous return increasing venous stasis in the lower limbs.
6 times risk increase
- Pulmonary embolus
renal system - what it dilated?
what is it dilated?
of the urinary collecting system due to relaxation of the smooth muscle of the ureter caused by progesterone as well as the mechanical compression by the growing uterus.
renal - what is more pronounced on the right.?
physiological hydronephrosi
renal - what rates increase?
Glomerular filtration rate and creatinine clearance - 50%
renal - the kidneys excrete more protein - what do they retain more of?
sodium ( and water).
renal - Secretion of what is increased? (3)
vitamin D, renin and erythropoietin is increased.
if there is no proteinuria, no infection and renal ultrasound and function is normal - what is more common?
- why is this caused?
Microscopic haematuria
- bleeding from the small vessels in the dilated renal function.
renal - what is common
Glycosuria
renal - infection common?
UTI - treat promptly with antibiotics known to be safe in pregnancy.
