5.1 Maternal Adaptations to Pregnancy Flashcards
[CVS] What is the mechanism by which stroke volume is increased during pregnancy?
Contributes more in the 1st half of pregnancy: by increased preload and reduced afterload:
• Increased preload: increased blood volume (↑ 40%) from changes in the haematological system (see below)
• Reduced afterload: reduced vascular resistance from increased progesterone and vasodilatory substances (prostaglandins, ANP, NO) → relaxes vascular smooth muscles → also ↓ BP
[CVS] What is the mechanism by which heart rate is increased during pregnancy?
Contributes more in the 2nd half of pregnancy: increased oestrogen levels → increases myocardial receptors
[CVS] What is the mechanism by which blood pressure is decreased during pregnancy?
Blood pressure decreases despite the increased cardiac output and blood volume due to decreased peripheral vascular resistance:
- Release of vasodilatory substances (e.g. progesterone, relaxin, prostacyclin)
- Softening of collagen fibres in vessels
- Low resistance through placenta (flow through low-resistance altered spiral arteries)
[CVS] How much is blood pressure changed during pregnancy?
SBP: Slight/no decrease (↓ 5 – 10)
DBP: Decrease (↓ 10 – 15)
The BP is the lowest in the 2nd trimester (24 – 28 weeks) then gradually rises to pre-pregnancy levels by term:
• Rise in 3rd trimester due to increased RAAS activation (↑ oestrogen and progesterone for labour) → very mild
[CVS] Heart is pushed up and left in the 3rd trimester due to upward pressure on diaphragm → ECG changes (ECG not routinely checked). What are the ECG changes seen?
- Sinus tachycardia (↑ ~15 bpm) – also fear and pain in labour
- Left axis deviation (due to ↑ LA/LV size + heart shift)
- Reduced PR interval
- Lead III: small Q wave & inverted T wave
- Inferolateral leads: ST depression* & inverted T wave
- Ectopic beats (more common in pregnancy)
[CVS] What happens to the veins draining lower limbs & pelvis during pregnancy?
Pressure from the uterus on the veins draining the legs and pelvis → varicose veins, haemorrhoids, peripheral oedema
1. Relative stasis of venous flow → increased risk of venous thromboembolism (VTEs; DVT/PE)
[CVS] What happens to the major abdominal vessels (when supine) during pregnancy?
IVC syndrome: heavy gravid uterus compresses on the IVC (90%) → obstructed venous return (8%) → reduced cardiac output:
- Reduced flow to the placenta (inefficient exchange)
- Hypotension → weakness, nausea, dizziness, syncope
- Some also have aortic compression → further hypotension
* Usually due to ineffective shunting of venous return through the paravertebral collateral circulation in pregnancy
[CVS] How is IVC syndrome managed in pregnancy?
left lateral tilt position (rather than supine) → when sleeping or if she collapses (even during CPR)
• Manual displacement of the uterus or tilting is used to relieve the weight of the uterus on the vena cava and aorta
• Towels/sheets under a transfer board or a wedge is used
[CVS] What pulse do you likely see in pregnant women?
Bounding/collapsing/waterhammer pulse, distended neck veins (more noticeable JVP)
[CVS] What heart sounds do you likely hear in pregnant women?
Increased splitting of heart sounds, 3rd heart sound, flow murmur (grade 1 or 2 murmur due to increased flow over valves with functional regurgitation → benign) → diastolic murmurs are not normal
[Heme]
RBC production increases and peaks at ____________ (up to 30% above non-pregnant values):
• Hormonal changes (____, _________, ___________) stimulate EPO release
• Dependent on adequate maternal iron stores
30 weeks;
progesterone, hCS/hPL, prolactin
[Heme]
Increased plasma volume is the major contributor to the increased blood volume observed (increases from 6 weeks and peaks at ____________):
• Greater increase in plasma volume than in RBC volume causes haemodilution → physiologic anaemia of pregnancy in late 2nd & 3rd trimester
• Most of the extra blood volume accounted for by increased capacity of _______________ → no evidence of circulatory overload
Pregnancy normal ranges: pregnant women have slightly lower _______________ levels on diagnostic tests (Hb ~12.5g/dL at term)
- not a disease state (should not have physical signs)
- Hb < 11g/dL investigate (likely due to IDA –> may require supplements)
~32 weeks
uterus, breast, kidneys, striated muscle, vascular systems;
haematocrit and Hb
[Heme] How is WBC affected during pregnancy and when is the effect peaked?
- increase
- labour
- Not inflammation or infection (more difficult to diagnose infection) → response to hormones or stress in labour
[Heme] How is platelets affected during pregnancy and when is the effect peaked?
- no change
- NA
- May be slightly low due to haemodilution (but still within normal pregnancy range)
[Heme] How is coagulation factors affected during pregnancy and when is the effect peaked?
- increase
- puerperium
- Hypercoagulability to minimise bleeding after delivery (increased factors I, VII, VIII, IX, X)
[Heme] How is coagulation inhibitors affected during pregnancy and when is the effect peaked?
- decrease
- Puerperium
- Increased thrombotic risk (decreased protein C/S)
What are the signs and symptoms pregnancy present with in the hematological system?
- Physiologic anaemia from haemodilution → no physical signs of anaemia
- Ankle oedema from volume augmentation (common in 3rd trimester)
- Different normal ranges for blood tests should be used
- Increased thrombotic risk (x2 in pregnancy; x5 in puerperium) → PE/DVT
[respi] Pregnancy is a hyperventilatory state (with 50% increase in minute ventilation from 8 weeks) → mainly driven by ____________:
𝐌𝐕=𝐕𝐓×𝐑𝐑
• Increased ____________ is main contributor → increased inspiratory reserve volume
• Respiratory rate does not increase
progesterone;
tidal volume
[respi] By what mechanisms does progesterone cause respiratory changes?
- Medulla respiratory centre: Increases chemoreceptor sensitivity to CO2 → increases minute ventilation
- Lung/bronchial smooth muscles: Directly induces relaxation of smooth muscles & bronchodilation → decreases resistance in airways
[Respi] How does an upward shift of diaphragm affect the respiration in pregnant women?
Decreased functional residual capacity, expiratory reserve volume & residual volume
• Forced expiratory volume (FEV1) remains unchanged
[Respi] How does an increased work done by diaphragm affect the respiration in pregnant women?
Diaphragm moves an additional 2cm (despite reduced physical space due to large uterus) → increased tidal volume (deeper breaths), inspiratory reserve volume, inspiratory capacity → no change in total lung capacity
[Respi] How does flaring outwards of lower ribs affect the respiration in pregnant women?
Thoracic diameter expands anteroposteriorly and transversely → increased thoracic circumference
[Respi] How does relaxation of thoracic ligaments & cartilage affect the respiration in pregnant women?
Relaxin mediates relaxation → broadens chest and increases the subcostal angle
[Respi] How does decreased chest wall compliance affect the respiration in pregnant women?
More inward movement of chest wall → reduced residual volume:
• Compliance of the lungs remains unchanged
[respi] There is a state of ______________ compensated by _________________ (ABG shows mild or no alkalosis) in pregnancy → favourable gradient for foetal offloading of CO2 to the mother:
- Slight rise in alveolar and arterial pO2 → increased O2 consumption to meet increased metabolic demands of both the foetus and mother
- Decrease in arterial pCO2 → increased minute ventilation and CO2 sensitivity
mild respiratory alkalosis ;
increased renal bicarbonate secretion
[respi] Increased progesterone levels causes ____________ and increased mucus production, relaxation of bronchiolar smooth muscles and decreased airway resistance:
• No changes observed in the respiratory examination (unchanged respiratory rate and FEV1 → FEV1 is used to assess ____________)
• Nasal congestion (due to mucosal hyperaemia and increased mucus secretion)
• Dyspnoea (due to ________________)
• Decreased peak flow and exercise tolerance
mucosal hyperaemia;
asthma in pregnant patients
increased CO2 sensitivity → triggers breathing drive
[renal] how does increased progesterone affect the renal system?
Relaxation of smooth muscles in the ureters, bladder, blood vessels:
• Dilation of ureters and renal pelves from week 7 of pregnancy
• Bladder tone reduces
• Kidneys enlarge by ~1cm due to dilated renal vessels and increased blood flow
[renal] how does mechanical pressure affect the renal system in the 3rd trimester?
3rd trimester: pressure from the enlarged uterus reduces bladder capacity
[renal] how does mechanical pressure affect the renal system in the late pregnacy?
Late pregnancy: pressure from the uterus, iliac arteries, and ovarian vein complexes compress the ureters at the pelvic brim
• Physiological hydronephrosis and hydroureter (80% of pregnant women)
• Right ureter tends to be more dilated than the left due to its more acute passage across the pelvic brim (more compressed)
• Causes urinary stasis and increased risk of UTIs and pyelonephritis (bacteria thrive in the reservoir of urine that accumulates in the dilated elongated ureters) → exacerbated by reduced ureteric peristalsis (due to increased prostaglandins in late pregnancy)
[renal] The main functional change that occurs in the renal system during pregnancy is raised GFR (by approximately 50% and remains stable until term) due to:
- ___________ (from early pregnancy → at least 50% above pre-pregnancy levels by term)
- ________________ (due to relaxin, NO, activation of RAAS)
The net effect of raised GFR is an increased solute load & thus increased solute excretion
Increased renal blood flow ;
Decreased renal vascular resistance
[renal] how is excretion of glucose affected in pregnancy?
Trace amount of glycosuria on dipstick (renal glucose load exceeds the renal threshold for glucose):
• Glucose tolerance tests are NORMAL (not a problem with carbohydrate metabolism)
• Unless there is more than trace glycosuria → possible diabetes that causes glucose intolerance
[renal] how is excretion of amino acids, urea, vitamins affected in pregnancy?
Increased excretion of these solutes → serum levels fall
• Pregnancy normal ranges must be used to interpret the renal panel!
[renal] how is excretion of bicarbonate affected in pregnancy?
Increased excretion to compensate for respiratory alkalosis
[renal] how is excretion of sodium and water affected in pregnancy?
Net retention of sodium & water to maintain homeostasis:
• Serum Na & K are largely unchanged → except for a slightly narrower normal range
[renal] how is excretion of protein affected in pregnancy?
No significant increase in urinary excretion of protein: • If proteinuria on dipstick → pre-eclampsia
[renal] Pregnant women tend to present with urinary frequency (defined as a subjective complaint of voiding too often during the day) and increased risk of UTI & pyelonephritis:
• Urinary frequency occurs due to compression of the bladder (by the gravid uterus) → presents with ______________________
o Incidence of stress incontinence increases post-delivery due to ______________
• Increased risk of UTI & pyelonephritis (renal inflammation) due to _______________
o Asymptomatic bacteriuria should be treated (associated with complications)
nocturia (interrupts sleep → fatigue) & stress incontinence (with laughing/sneezing due to decreased bladder tone);
stretching or damage to pelvic floor muscles;
urinary stasis
[gi] what are the functional changes of the gi tract during pregnacy?
Increased appetite:
• Progesterone is orexigenic
• Oestrogen is anorexigenic (thus appetite decreases near term)
Reduced gut motility:
• Progesterone causes generalised smooth muscle relaxation & reduced peristalsis
Increased brush border enzyme activity
[gi] what are the physical changes of the gi tract during pregnacy?
- Weight gain* (mostly fluid + fat)
- Displacement of stomach & bowel (by gravid uterus
- Increased height of duodenal villi
[gi] Why does morning sickness occur in pregnant women?
Nausea & vomiting caused by hCG & progesterone acting on the hypothalamic vomiting centre → gastric smooth muscle relaxation → reduced motility:
• Resolves by 16 weeks of pregnancy
• Hyperemesis gravidarum (severe vomiting causing dehydration & significant weight loss) requires hospitalisation and acute treatment
[gi] Why does heartburn occur in pregnant women?
Acid reflux into the lower oesophagus due to:
• Increased intra-abdominal pressure
• Displacement of stomach and diaphragm (causing loss of angle of His that strengthens the LOS)
• Progesterone-induced smooth muscle relaxation (reduced LOS tone)
[gi] Why does constipation occur in pregnant women?
Due to reduced gut motility, increased water absorption from stool & compression of sigmoid colon & rectum:
• Straining due to constipation can worsen haemorrhoids (already common in pregnancy due to increased venous pressures)
[gi] Why does gallstones occur in pregnant women?
Due to biliary stasis from reduced contractility of gallbladder & effects of oestrogen on bile acid transport
[gi] Why does gingivitis occur in pregnant women?
Due to high hormone levels causing increased vascularisation, oedema, and friability of the gums
[gi] what are the signs of hyperextrogenism seen in pregnant women on abdo exam?
Signs of hyperoestrogenism (in normal patients, these signs are associated with chronic liver disease):
• Obvious abdominal distension
• Spider naevi (in distribution of the SVC)
• Palmar erythema
*Liver is largely unchanged in size & function (mild hepatomegaly may be missed due to upward displacement)
[immuno] what is the result of reduced chemotaxis in pregant women?
- Reduced risk of foetal rejection
* Increased risk of Gram-negative infection
[immuno] what is the result of reduced NK cell activity in pregant women?
- Reduced risk of foetal rejection
* Increased risk of listeriosis & toxoplasmosis
[immuno] what is the result of increased monocytes and granulocytes in pregant women?
• Improved phagocytosis → increased clearance of foetal cells from maternal blood
[immuno] what is the result of increased polymorphs in pregant women?
• Improved protection against bacteria
[immuno] what is the result of iIncreased opsonisation (by fibronectin & complement) ?
• Improved protection against bacteria
[immuno] what is the result of Reduced Th1 response & cytokines (TNF-α/β, IFN-γ, IL-2) in pregant women?
- Reduced foetal rejection
* Increased risk of fungal & viral infections
[immuno] what is the result of Enhanced Th2 response & cytokines (IL-3, IL-4, IL-6, IL-10) in pregant women?
• Improved antibody response
[immuno] Due to the above changes in the immune system, pregnancy tends to present with:
• Increased risk of some infections (e.g. intestinal parasites, Gram-negative bacteria like ______________, protozoal infections like ____________) o Avoid risky foods (e.g. raw meat, eggs), malaria prophylaxis in endemic areas
o May be offered flu vaccination to protect against influenza
• Improvement of some autoimmune conditions (e.g. multiple sclerosis, rheumatoid arthritis, ulcerative colitis) → may have __________________
listeriosis, toxoplasmosis;
malaria;
post-partum rebound exacerbation
[skin]
Hyperpigmentation (may also be seen in women on OCPs):
• On the face (called ___________), areolae, linea alba ( called _______________)
• Early pregnancy: ______________ acts on melanocytes to initiate these changes
• Late pregnancy: ______________________ darken the existing changes
• Typically resolve spontaneously after pregnancy
choloasma;
linea nigra;
oestrogen and progesterone;
other hormones (e.g. ACTH, placental CRH)
[skin]
Striae gravidarum: Wide _______________ on the abdomen, breasts, thighs which eventually fade to silvery white after pregnancy:
• Hormones (oestrogen, relaxin, ACTH, glucocorticoids) reduce adhesion between collagen fibres & encourage formation of ________________ to further separate fibres
• Increased ______________ in the skin lyse collagen → allows for rapid stretching of dermis by the growing uterus
• Never completely disappear → may be unsightly & upsetting for some women
violaceous linear marks;
mucopolysaccharide;
mast cells
[skin] why is there pruritus in pregnant women?
Particularly on the stretching abdomen
• May also be a sign of liver or skin disorders → should be examined & investigated if needed
[skin] why is there acne in pregnant women?
Due to increased sebaceous gland secretions caused by increased ovarian & placental androgens
[skin] why is there prickly heat/ rash in pregnant women?
Due to increased dilation of cutaneous blood vessels & activity of eccrine sweat glands (mainly on palms & soles):
• Caused by increased metabolic activity that generates hea
[skin] why is there thicker hair in pregnant women?
Due to oestrogenic effects causing a prolonged anagen phase: • Telogen effluvium: postpartum drop in hormone levels causes a higher percentage of hair to enter the telogen (resting & shedding) phase simultaneously → clumps of hair loss (usually temporary)
