WCS15 Physiology Of Pregnancy & Minor Ailments Flashcards
Physiological changes in pregnancy
- Respiratory system
- Cardiovascular system
- Haematological system
- Endocrine system
- Renal system
- GI system
- Hepatobiliary system
Physiological adaptation of pregnancy
- Proactive (rather than reactive)
- Maintain safe environment for fetus
- Provide extra energy, nutrition, oxygen needed to support fetal growth
- Respiratory system
Mechanical effects
- enlarging uterus
- hormonal changes + increasing laxity of thoracic ligaments
—> affect anatomy of thoracic cage
Biochemical: ↑ Progesterone —> ↑ O2 consumption + ↑ Tidal volume
Mechanical: Enlarging uterus —> Elevate resting diaphragm position + ↑ Abdomen size + ↑ Ribcage size
- Lifting of rib cage with upward flaring of ribs
- ↑ AP + Transverse diameter
- ↑ Lower chest wall circumference
- ↑ Costal angle - Elevation of diaphragm
- Uterus displaces diaphragm superiorly at term
- function remains normal, excursion not reduced - ↑ Oxygen consumption
- by 20% (30-40 ml/min) from baseline level of 220 ml/min to support:
—> Extra cardiac, renal, respiratory work of mother
—> Uterine, breast development of mother
—> Metabolism of feto-placenta unit - ↑ Ventilation
- by 40% - ↑ Tidal volume
- by 40%: 500 —> 700 ml - ***No change in respiratory rate
- ↓ Maternal pCO2
—> to allow more efficient placental transfer of CO2 from the fetus
- maternal pCO2: 4.8 kPa —> 3.7 kPa
- fetal pCO2: 7.3 kPa
Clinical relevance of Respiratory system
Dyspnea during normal pregnancy is common (even in early pregnancy when uterus is still small), mechanism not clear
—> Progesterone-induced hyperventilation
—> Dyspnea during pregnancy correlated with low pCO2
- Cardiovascular system
- ↓ Systemic vascular resistance —> ↓ Afterload
- ↓ 35-40% baseline - ↑ Plasma volume —> ↑ Preload
- ↑ HR
- progressively throughout pregnancy by 10-20 bpm, max in 3rd trimester - ↑ SV
- ↑ CO
- 30-50%, sharpest rise in CO occurs by beginning of 1st trimester, continued increase into 2nd trimester, further ↑ during labour - ↓ SBP, DBP
- ∵ ↓ PVR
- to lowest point during 2nd trimester (5-10 mmHg below baseline)
- gradually ***↑ during 3rd trimester to near pre-pregnant level at term
Clinical relevance of Cardiovascular system
- Ejection systolic murmur may be detected from mid-trimester (flow murmur) due to hyperkinetic state of CVS system
—> check if murmur changes with position (not change with position) - More common for Gestational hypertension / Pre-eclampsia to be diagnosed in 3rd trimester
- Unusual if BP starts to rise during mid-trimester even though it is still below 140/90 mmHg
- Haematological system
- ↑ Plasma volume
- starting at 6-8 weeks
- ↑ progressively until 30-34 weeks - ↑ RBC mass
- by 20%
- ***↑ erythropoiesis (provided that mother has normal nutrition + sufficient Fe / vitamin supplement) - Plasma volume ↑ > RBC mass ↑
- physiological anaemia from haemodilution —> ***↓ Hb, Hct, RBC count - ↓ Hb, Hct, RBC count
- ↑ WBC (↑ Neutrophil)
- ↓ Platelet count
- Haemodilution effect
- Increased fibrinolysis physiologically within uteroplacental circulation to maintain blood flow - ↑ Procoagulatory factors
- Factor 7, 8, 10, fibrinogen - ↓ Antithrombin III, Protein S
- inhibitor of coagulation
Benefits of Hypervolaemia + Anaemia
- ↓ Blood viscosity
—> ↓ resistance to flow
—> ↑ placental perfusion + ↓ Cardiac work - ↑ Blood volume
- provide reasonable reserve against blood loss during delivery / post-partum haemorrhage
Clinical relevance of Haematological system
- Note Hb level at booking visit + Repeat Hb later in pregnancy (28-32 weeks)
- woman may become ***anaemic in later part of pregnancy - Watch out for ***Venous Thromboembolism (∵ Pregnancy pro-coagulatory)
- esp. if other risk factors e.g. prolonged bed rest - Expansion in plasma volume is relatively less in women with pre-eclampsia
- watch out if woman has ***static / increasing Hct - Thrombocytopenia due to pregnancy
- 8-10% of normal pregnancy
- Endocrine system
Increased metabolic needs during pregnancy
1. ↑ Thyroxine-binding globulin
- ↑ Total T4, T3
- by 50% during 1st half of pregnancy
- plateauing at ~20 weeks of gestation - No change in free T4, T3
- hCG has weak thyroid-stimulating activity
- peaks at ~12 weeks
—> ↓ TSH / ↑ free T4, T3
Clinical relevance of Endocrine system
- Transient (usually Subclinical) hyperthyroidism should be considered normal
- Use Trimester-specific reference range during pregnancy
- Renal system
- ↑ Kidney size
- 1 cm in length
- volume ↑ up to 30%
- marked dilatation of calyces, renal pelvis + ureters in most pregnant women due to ***hormonal factors (just like enlarging uterus in later pregnancy) - ↑ Renal plasma flow
- by 60-80% - ↑ GFR
- by 50% over non-pregnant women by the end of 1st trimester - ↓ Serum Cr, Ur level
- ↓ Reabsorption of glucose
- ↑ Excretion of glucose across glomerulus
- by 10x
Clinical relevance of Renal system
- Physiological hydronephrosis + hydroureter during pregnancy
- usually more over right side - Glycosuria by dipstick testing is common in pregnancy
- may be present in the absence of hyperglycaemia / renal disease
- GI system
Relaxation of smooth muscle:
- ↑ Intragastric pressure
- ↓ Lower esophageal sphincter pressure
- ↓ Gastric peristalsis
- ↓ Gastric emptying
- ↑ Small + Large bowel transit time (↑ H2O absorption from gut)
Clinical relevance of GI system
- Gastro-esophageal reflux
- N+V
- Constipation
—> Normal in pregnancy
- Hepatobiliary system
↑ Liver metabolism in pregnancy
- ↑ ALP
- ↑ with gestation (∵ placental production)
- 2-4 fold by term, max 400 U/L in 3rd trimester
- therefore may not be reliable when look at total ALP - ↓ GGT
- ↓ Albumin
- by 20-40%
- partially dilutional by ↑ blood volume (contribute to most of fall in total serum protein) - ↓ Bilirubin
- ***No change in bile acid, ALT, AST
Clinical relevance of Hepatobiliary system
Caution with interpretation of lab results
- e.g. ALP in pregnancy may not be reliable
—> need specific tests (isoenzymes to distinguish ALP from placenta from other source) to exclude liver / bone cause
Minor ailments of pregnancy
- not life-threatening
- discomfort + distress
- due to adaptation of maternal body
- many caused by ***Progesterone on smooth muscles / CT of body
- N+V
- Heartburn
- Constipation
- Fainting / Dizziness
- Varicosities (varicose veins, haemorrhoids, vulval varicosities)
- Backache
- Leg cramps
- Carpal tunnel syndrome
- Subluxation of pubic symphysis
- Urinary frequency
- N+V (Morning sickness)
- Onset always in 1st trimester
- usually till 12 weeks
- 70% of pregnant woman
- Severe: Hyperemesis gravidarum
Etiology:
- Unknown
- Various contributory factors proposed
- Associated with ↑ hCG
Prevention / Treatment:
- Dietary / Lifestyle change
- Avoid trigger
- **Light snacks instead of large meal
- **Avoid Fe supplements
- Seek medical advice if severe —> need to correct electrolyte + fluid imbalance
- ***Anti-emetics
—> Dimenhydrinate, Promethazine (H1 receptor antagonist)
—> Metoclopramide (Dopamine antagonist + UGI motility stimulants)
- Heartburn
50% of pregnant women
Related to:
- Relaxing effect of ***progesterone on cardiac sphincter
- ↑ intragastric pressure due to growing uterus
- Flattening of diaphragm distorts the shape of stomach + ↓ angle at the gastroesophageal junction
Prevention / Treatment:
- Dietary modification: **small, frequent meals, low in spices, avoid food that lower sphincter pressure e.g. **chocolate, coffee, alcohol
- Elevate head of bed: sleep in ***upright position by additional pillows
- ***Antacids: taken after meals + at bedtime
- Constipation
May lead to haemorrhoids —> further increase constipation due to fear of pain
Etiology:
- ↓ Gut motility by progesterone
- ↑ H2O absorption from gut due to ↑ gut transit time
- Oral Fe supplement
Prevention / Treatment:
- ↑ Dietary fibre
- Adequate fluid intake
- Moderate exercise
- Maintain regular bowel habit
- Stool softener / Laxative
- Fainting / Dizziness
Insufficient blood / O2 to the brain
Etiology:
- ↑ Vasodilatation due to ***progesterone on smooth muscle
- Standing ***erect for long time
- **Supine hypotension:
- ↓ CO due to ***↓ venous return caused by pressure of gravid uterus on vena cava when supine
Prevention / Treatment:
- Get up slowly after sitting / lying down
- If feel faint —> find a seat
- ***Avoid total supine position, turn to lie on side if starts to feel faint
- Varicosities (varicose veins, haemorrhoids, vulval varicosities)
Etiology:
- Relaxing effect of progesterone of smooth muscles of venous wall
- Aggravated by growing uterus —> **Pelvic congestion + **Poor venous return
- Constipation
Prevention / Treatment:
- Haemorrhoids
- prevention / treatment of constipation
- topical medication e.g. Anusol suppositories
- surgery NOT performed - Varicose veins
- avoid prolonged standing
- exercising leg muscles
- ***elevation of legs
- support stockings - Vulval varicosities
- sanitary pad / panty girdle for support
- caution when ***cutting the episiotomy
- Backache
50% of pregnant women
Etiology: - ↑ Lumbar lordosis causing strain on back muscles - Ligamentous laxity due to hormone —> ***Progesterone —> ***Relaxin
Prevention / Treatment:
- sit on comfortable chair who support both back + thighs
- stand tall with abdomen + buttocks tucked in
- wear flat shoes for even weight distribution
- sleep on good mattress to ensure equal pressure on all parts of body
- care taken when changing from lying down to avoid straining the back muscles —> arms should be used to pushed up into sitting position
- avoid lifting heavy objects
- Leg cramps
- Often at night
- can be very painful
- more common during 3rd trimester
Etiology:
- Unknown
Prevention / Treatment:
- Regular gentle exercise, esp. ankle / leg movements to improve circulation
- Mg, Ca, non-pharmacological treatment options can be used for relief of leg cramps in pregnancy, based on woman’s preferences / available options
- Carpal tunnel syndrome
- numbness / tingling in fingers / hands
- worse at night
- common in 2nd, 3rd trimester
Etiology:
- **Fluid retention + **Swelling of CT which compresses median nerve in wrist
Prevention / Treatment:
- Elevate hand
- Noctural wrist ***splinting
- Physiotherapy
- Subluxation of pubic symphysis
- Suprapubic pain, Tenderness, Swelling, Edema
- worse upon weight-bearing, walking, climbing stairs, turning in bed, changing posture
Etiology:
- Pubic symphysis widens due to ***Relaxin —> ↑ mobility
- Mechanical strain
Prevention / Treatment:
- Rest
- Pelvic support
- Analgesia
- Urinary frequency
- Affect most during 1st (growing uterus pressing on bladder), 3rd trimester
Etiology:
- Pressure from growing uterus on the bladder
- ↑ reabsorption of Na, H2O —> ↑ need to pass urine esp. at night (i.e. Nocturia)
Prevention / Treatment:
- ***Fluid restriction in the evening with ↑ fluid intake earlier in the day
- Limited intake of natural diuretics e.g. Caffeine