Physiology in Pregnancy Flashcards
What are the general changes in the body associated with pregnancy?
Mechanical
Metabolism
Fatigue – particularly early pregnancy
Heartburn/reflux
Oedema
Breasts
Thyroid
General state of immunosuppression
Weight gain
What happens to metabolism?
Anabolic then quickly becomes catabolic to allow nutrient supply to the foetus
Do you get insulin resisitance?
Yes-almost 2x increase in insulin
What can occur due to the increase in triglyceride breakdown?
Can get starvation Ketoacidosis-within 24-48 hrs can become very acidotic when pregnant & this happens
DKA is very dangerous in preg and can result in what?
IUD
What rate doubles in preg?
BMR
What is gestational diabetes?
Insulin resistance & hyperglycaemia of pregnancy
More likely to develop T2DM (should be checked once a year-mitigate risk with lifestyle factors)
What are the 3 things associated with Preeclampsia?
- High BP
- Oedema
- Proteinuria
What percentage get oedema & is this always physiological?
70-80% get oedema- physiological mostly but can be indicative of pathology such as pre-eclampsia
When do significant changes occur to the CV system?
Early in the first trimester
By how much does circulating BV increase?
50-70% of non pregnant
Does systemic vascular resistance increase or decrease?
DECREASE-maximal at 20-32 weeks
Do each of these increase or decrease?
1. Blood flow
2. CO
3. SV
4. HR
5. 02 consumption
- Increases
- Increases
3, Increases (SVxHR=CO) - Increases
- Increases
ALL INCREASE
What happens to CO in supine position?
25% reduction in CO
What do prostacyclin’s do?
Decrease systemic vascular resistance
In what trimester does BP tend to drop?
BP tends to drop in middle trimester & then rise-those who don’t drop are more inclined to be the ones to have pre-eclampsia
What are the intrapartum CV changes that occur?
-Autotransfusion of contractions
-Pain-increasing catecholamines
-CO increases by 10% in labour & by 80% in 1st post delivery hour (then continues to fall over the next 24 weeks)
When in the post partum period do CV changes return to normal?
3 months (mostly)
BV decreases by how much 3 days post delivery?
10%
How does BP adjust in the postpartum period
BP initially falls then increases again days 3-7(pre preg levels by 6 wks)
What happens to SVR & HR in the postpartum period?
-SVR increase over first 2 wks to 30% above delivery levels
-HR returns to pre preg over 2 weeks
Minute ventilation increases by what?
40-50%
Do these increase or decrease?
1) O2 demand
2) RR
3) TV
4) FRC
5) PCO2
1) INCREASE
2) INCREASE
3) INCREASE
4) DECREASE
5) DECREASE
What happens to PEFR & FEV1?
UNCHANGED
What is the foetuses respiratory system?
Placenta
What happens to thoracic circumference when the diaphragm moves up?
Thoracic circumference increases (May get splaying of ribs)
What happens to the acid base balance?
C02 will be increased & PO2 tends to sit higher
What happens to the O2Hb dissociation curve?
Shifts to the right-decreased affinity for oxygen
What happens to the urinary collecting system & where is this more pronounced?
Dramatic dilation-more pronounced on right (more effected by hydronephrosis)
Physiological Hydronephrosis
Due to relaxation of the smooth muscle of the ureter caused by progesterone as well as the mechanical compression by the growing uterus
..?.. renal plasma flow – 60-80% by end of second trimester settling to 50% increase through the third trimester
INCREASED
GFR ..?.. & creatinine clearance ..?.. by up to 50%
INCREASES (both)
Means normal levels of urea & creatinine are much lower during pregnancy
..?..uria is common
Glycosuria
Microscopic ..?.. may be present
Haematuria (can be the result of the progesterone)
Does protein excretion increase?
YESSS
What increases with increasing gestation?
URATE
UREA ..?.., Creatinine ..?..
BOTH DECREASE
Urethra shortens: what does this mean for UTI risk and ability to empty bladder?
More risk of UTI & also harder to empty bladder as easily
UTIs should be treated promptly with Abx which are known to be safe in pregnancy
What increases compared to birthweight?
PV
Hb, Haematocrit and RCC all do what in pregnancy?
DECREASE
Is there any change to MCV or MCHC?
NO Change
Platelet count increases: True or false?
FALSE
Platelet count decreases
2-3 fold increase in the requirement for what?
IRON
10-20 fold increase in what requirements?
FOLATE Requirements
What supplement reduces the risk of conditions like spina bifida?
FOLIC ACID
WCC Increase: True or false?
TRUE (& neutrophil count is increased - a WCC of up to 16x109/L is normal in pregnancy)
In terms of Haematological changes what kind of state is pregnancy?
Hypercoagulable state
These changes in the coagulation system occur from very early in pregnancy and can persist for up to 6 weeks after delivery. Half of all blood clots associated with the antenatal period occur in the first 15 weeks of pregnancy.
Why are pregnant people more prone to back pain during (and after) pregnancy?
Wth weight gain, an increased BV & enlarging fetus, the centre of gravity no longer falls over the feet. So as to not be constantly falling over, the pregnant person needs to lean backward and the curves of the spine change along its whole length
What hormones cause increased pliability & extensibility of connective tissue?
Relaxin (hormone produced during pregnancy) & increased levels of oestrogen & progesterone
Ligamentous joints become less stable during pregnancy: What joints are particularly affected to allow for the birth of the baby?
Symphysis pubis & sacroiliac joints
The normal pubic symphyseal gap of 4-5mm increase on average by what?
Another 3mm
When does joint loosening occur & when should it return to normal?
Starts as early as 10 weeks but should return to “normal” 4-12 weeks post partum
By term there is an increased load on the ..?.. joints of 2.8 times the normal value when standing.
HIP
BMR increases in pregnancy. During pregnancy metabolism changes to ensure what?
Adequate nutrition for foetal growth
Why is pregnancy a time of relative insulin insensitivity?
Human placental lactogen produced by the placenta acts against maternal insulin
Why is there an increased storage of lipids in maternal tissues?
FAs are vital for foetal organogenesis
What weight gain throughout pregnancy would be considered normal?
10-14kg
What is the likely reason for fatigue & when is it at its worse?
Can be overwhelming during the first trimester
Likely due to hormonal changes
Tends to get better in the second trimester.
It often returns towards the end of pregnancy when it is more likely due to the increased work load of advanced pregnancy, discomfort and difficulty sleeping.
What are the causes of Heartburn/reflux in pregnancy?
During pregnancy food moves more slowly into the stomach & there is delayed emptying.
Hormones also cause relaxation of the lower oesophageal sphincter so contents are more likely to reflux from the stomach back into the oesophagus.
The mechanical pressure from an enlarging uterus makes this worse as does delayed gastric emptying.
Why is heartburn/reflux in pregnancy one of the reasons why GA is much higher risk in pregnancy?
Changes mean the risk of aspiration is much higher and increases with advancing pregnancy.
The introduction of regional anaesthesia (spinals and epidurals) made a huge difference to morbidity and mortality of operative procedures in maternity patients.
Why do 80% of pregnant people develop some oedema particularly towards term?
Physiological sodium & water retention & decreased ability to excrete sodium & water load
Increased BV & decreased VR due to compression of IVC from the gravid uterus also contributes to peripheral oedema
What happens to the breasts in pregnancy?
Increase in size & vascularity & become warm, tense & tender
Increased pigmentation of the areola & nipple & a secondary areola appears
Montgomery tubercles appear on the areola
What can be expressed from the breasts from the end of the 3rd month?
Colostrum like fluid
Why do Free T3 & T4 (active) levels remain the same even though the liver produces more thyroid binding globulin (TBG)?
Total level of Thyroxine (T4) & triiodothyronine (T3) also increase
Why is pregnancy associated with relative iodine deficiency?
Maternal iodine requirements increase because iodine is actively transported to the fetoplacental unit and urinary iodine excretion is doubled because of an increased GFR 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 condition can be associated with a biochemical hyperthyroidism (increased levels of T4 & suppressed TSH) & why is this?
Hyperemesis gravidarum
Beta sub unit of BHCG (a pregnancy hormone) is structurally very similar to TSH
This biochemical hyperthyroidism will resolve with the hyperemesis.
What if necessary can be used for symptom control of tachycardia caused by the high levels of T4?
Beta Blockers
Thyrotoxicosis (overactive thyroid) occurs in approximately 1 in 500 pregnancies. It is most often due to what?
Graves disease (autoimmune disorder)
The antibodies that cause Graves disease (TSH receptor antibodies) can cross the placenta and cause fetal and/or neonatal hyperthyroidism.
Why is it important to ensure good thyroid replacement prior to pregnancy in those with Hypothyroidism?
Fetus is dependent on maternal thyroid function until fetal thyroid function begins at around 12 weeks gestation
Why in pregnancy is there a general state of immunosuppression?
To allow for foetal tollerance
Why in pregnancy is there a general state of immunosuppression? How does this affect the mother?
To allow for foetal tolerance
It unfortunately increases the maternal susceptibility to infection.
This explains why some autoimmune conditions such as Crohns disease, rheumatoid arthritis, can improve during pregnancy.
What are examples of organs that have increased oxgen requirements?
Uterus & breasts
The heart has to work harder during prenancy because of?
The growing fetus, the weight gain associated with pregnancy and the increased oxygen requirements of the uterus and breasts. The heart also has to pump blood through the utero placental circulation.
When do CV changes return to normal?
Postnatally once all pregnancy associated changes have returned to prepregnancy levels
Challenge to the CV system means that in pregnancy people with cardiac disease may experience what?
Can suffer significant complications that may lead to maternal & foetal death & previously undiagnosed cardiac disease may come to light
What is the leading indirect cause of maternal death in the UK?
Cardiac disease
What causes the physiological anaemia of pregnancy?
The circulating blood volume increases by 50-70% of the non pregnant. Red cell mass also increases but only by about 40% causing a relative haemodilution
Why is left ventricular end diastolic volume increased and when can this be seen?
Due to the increase in circulating BV
Can be seen as early as 10 weeks on ECHO
For those with what conditions can increased BV cause problems for?
Dilated cardiomyopathy or lesions such as mitral stenosis or pulmonary hypertension.
What happens to 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
How is systemic vascular resistance (SVR) calculated?
Mean arterial pressure (MAP) – mean venous pressure (MVP)/ Cardiac output (CO)
Why does SVR drop?
Increased circulating vasodilators and the diversion of blood into the low pressure uteroplacental unit.
How much does blood flow to the kidneys increase by?
60-80%
What are warm, red hands and feet caused by?
Increased blood flow
What does increased blood flow to the nasal mucosa increase the risk of?
Nose bleeds during pregnancy as well as a sensation of stuffiness or congestion
How is CO calculated & does it increase?
The cardiac output is also increased because the stroke volume – the amount of blood pumped out by the ventricle with each beat - is increased. The heart rate also increases.
Cardiac output = stroke volume x heart rate
Cardiac output increases by approximately 30-50% by the end of the second trimester
People who cannot increase their CO such as those with ..?.. are at risk
Aortic stenosis
By term what is the HR of a pregnant person?
Usually approx 10-20 beats higher
Whilst a sinus tachycardia is not uncommon what other pathologies causing tachycardia shoul be considered depending on the clinical context?
- Hypovolaemia
- PE
- Sepsis
During pregnancy oxygen consumption can increase by 20-30% by term. Why is this & to whom is this a risk?
Myocardium has to work harder & therefore requires more 02.
For people with coronary artery disease (older/obese/diabetic/smoker) there is a risk of pregnancy triggering ischaemic heart disease and myocardial infarction.
Why would any pregnant person lying supine lose 25% of their CO?
Vena caval compression by the pregnant uterus
NEVER LIE A PREGNANT PATIENT FLAT – they will faint.
In what position should resuscitation occur in the event of a maternal collapse/cardiac arrest ?
A pregnant patient 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.
Intrapartum CV changes:
What is autotransfusion of contractions?
Pain?
With every contraction up to another 500 mls of blood is dumped into the circulation
Pain – increases circulating catecholamines and increases the heart rate, blood pressure and cardiac output (CO =SVxHR)
During labour CO increase by a further 10% and immediately after delivery can increase to 80% above the already increased CO of pregnancy. What causes this?
Lack of uteroplacental unit to be supplied but also because of the immediate relief of inferior vena caval compression.
By when do most CV changes return to normal?
By 3 months post delivery
3 days post delivery the blood volume will have decreased by what?
10%
The blood pressure (BP) initially falls then increases again by 3-7 days after birth. When does it return to normal?
The BP returns to prepregnancy levels by 6 weeks
What happens to SVR & HR in the postpartum period?
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.
How is there increased O2 availability & CO2 removal in the mother & the foetus?
Physiological adaptions during pregnancy increase the volume of air & gas exchange of each breath
TV increases & there is a 40-50% increase in ..?…
Minute ventilation
RR increases & can be perceived as what & what happens because of this relative Hyperventilation?
SOB (dyspnoea)
PCO2 levels are lower in pregnancy and the pregnant healthy person is in a state of compensated respiratory alkalosis.
Enlarging uterus does what to the diaphragm and lower thorax?
The enlarging uterus pushes up the diaphragm by as much as 4cm and increases the diameter of the lower thorax by 2cm by splaying the lower ribs
Enlarging uterus does what to the diaphragm and lower thorax?
The enlarging uterus pushes up the diaphragm by as much as 4cm and increases the diameter of the lower thorax by 2cm by splaying the lower ribs
FRC reduces: How is it further reduced?
Supine position (another reason not to lie a pregnant person flat)
Why in some pregnancies does asthma improve?
Bronchodilator effect of the progesterone
At 28 weeks a Hg of 105 g/L or above is considered normal (non pregnant reference range 120-160g/L) why is this?
Physiological anaemia of pregnancy
PV increases proportionate to what?
Birthweight
What happens to platelet count in pregnancy?
Because of the increase in plasma volume there is a relative decrease in platelet count during pregnancy but generally platelet counts remain within normal limits for the non pregnant patient.
What is the most common haematological abnormality of pregnancy?
Fe deficiency anaemia
It is more common in twin (or more) pregnancies.
Going in to pregnancy with depleted Fe stores is common and may be due to what?
Menorrhagia, inadequate diet, previous recent pregnancies. Post partum haemorrhage (2-5% of deliveries) contributes to iron deficiency postnatally.
Fe deficiency in pregnancy is also associated with intrauterine growth restriction.
What is the second most common cause of pregnancy anaemia?
Low serum levels of folate (however liver levels of folate are maintained)
What increases & decreases in pregnancy to make it a hypercoagulable state?
Clotting factors VII, IX and X increase as does fibrinogen.
Protein S and C and anti thrombin 3 levels decrease.
Fibrinolytic activity decreases.
What causes increased risk of DVT apart from hypercoagulable state?
Venodilation and reduced venous return increasing venous stasis in the lower limbs.
What is one of the main causes of direct maternal mortality in the UK killing 6-15 people per year in preg or the puerperium?
PE
Preg increases the risk of thromboembolism by 6x
The kidneys excrete more protein but retain more what?
Sodium & H2O
Secretion of Vit D, renin & erythropoietin is …?
INCREASED
Microscopic haematuria is more common if what conditions are met?
More common and if there is no proteinuria, no infection and renal ultrasound and function is normal, is most likely due to bleeding from the small vessels in the dilated renal function.
Is underlying kidney disease likely to worsen or get better?
Is likely to worsen during pregnancy because of the additional work being done by the renal system.
Why is testicular temp lower than body temp?Tp
To facilitate sperm production
What is the role of the epididymis?
Storage site for sperm-remains there for ~ 3 months
Seminal vesicles and prostate create what fluid?
Semen
What is the fibrous capsule around the testis?
Tunica albuginea
Where is the site of sperm production?
Seminiferous tubules
What are the 3 types of cells within the seminiferous tubules? And what is their role?
Germ cells- produce sperm
Sertoli/sustentacular cells- support sperm producing cell, produce inhibin
Interstitial(Leydig) cells- produce testosterone
What cells produce testosterone?
Leydig cells
What is the average time from production of sperm to ejaculation?
Sperm cycle-64 days (millions of viable sperm per day)
What is the role of testosterone production?
- For male secondary sexual characteristics
- Controls spermatogenesis
What is the role of testosterone production?
- For male secondary sexual characteristics
- Controls spermatogenesis
What are the reproductive hormones responsible for the endocrine control of testicular function?
GnRH- Gonadotrophin releasing hormone, produced from hypothalamus
Gonadotrophins- FSH and LH, released from anterior pituitary
Testosterone- released from testicles
Where is testosterone released from?
Released from the testicles
Where is GnRH released from?
Hypothalamus
Where is FSH & LH released from?
Anterior pituitary
What can happen if take external hormone supplements?
May affect fertility as own hormone access will be supressed
What is spermatogenesis and what is the average cycle length?
- Sperm production from the primordial germ cells (present in the seminiferous tubules of the testicle)
- Average cycle of spermatogenesis is 64 days in which the germ cells pass through different developmental stages
What are the 2 distinct phases during spermatogenesis/development?
- Spermatocytogenesis (clonal expansion and maturation through mitotic & meiotic process)
- Spermiogenesis-differentiation into mature sperm cells
Process starts at puberty and continues lifelong
What are spermatogonia?
Immature germ cells
what are the factors affecting spermatogenesis that can lead to male infertility?
Medical or lifestyle or a combination
What are the medical problems that can affect spermatogenesis?
Pretesticular-Problem with the hormonal control
Testicular- Problem at the site of production
What is Kallman’s syndrome?
Isolated deficiency of GnRH production from the hypothalamus
What is an orchidopexy?
Operation for replacing an undescended or maldescended testicle
Smoking and obesity are major risk factors - what can smoking in particular impact in males?
Impacts the sperm production as well as the functional capacity of the sperm
What are steps that can be taken to reduce the impact of factors affecting fertility?
Improve lifestyle- normal BMI, stop smoking, alcohol in recommended limits, healthy diet, exercise, adjustments to occupational exposure
Optimise underlying medical condition
Stop medications or switch to alternative pregnancy compatible medications
Reduce STI risk and treat promptly if diagnosed.
Fertility preservation- sperm freezing prior to surgery or cancer treatment
How many sperm should there be per ml and what should motility be?
Should be about 15 million/ml or more & motility should be about 32% of good swimming sperm in whole sample
What are androgen deficiency symptoms?
Infrequent shaving, unable to grow a beard, low libido, erection/ejaculation difficulty
What can working in high heat environments do to the scrotum?
Can raise the temp of the scrotum and the testicles and hence can impair sperm production
What examinations are done for male infertility issues?
BMI
Genital examination- external genitalia, testicular size, palpation of vas deferens, inguinal hernia, varicocoele
USS testis
Hormonal profile- FSH, LH, Testosterone, Prolactin
Genetic test- Karyotype, Y-chromosome microdeletion
What is an absent vas deferens a feature of?
CF (CF might not show any phenotypical features if you are a carrier)
Small testicle may show infertility. True or false?
True
Oligospermia could be due to what factors?
- Hormonal
- Lifestyle
- Genetic
- No cause (idiopathic)
What could be the causes of amenorrhoea?
- Problem with regulating hormones (Hypothalmic or pituitary cause -hypogonadotropic hypogonadism(Low FSH, LH, high prolactin))
- Problem with ovarian function (Hypergonadotropic hypogonadism- high or normal FSH, LH)
- Problem with uterus or outflow tract (congenital or iatrogenic)
What is the difference between primary and secondary amenorrhoea?
Primary=never had a period (menarch=onset of bleeding at puberty)
Secondary= stopped bleeding for 6 months or more
