6.2: Physiological adaptations in pregnancy Flashcards
What ‘red flags’ would you be looking for in a history and examination during antenatal screening and what will it help you determine?
- Baby’s risk of acquiring genetic diseases (FH)
- Maternal lifestyle; smoking and alcohol
- Mother’s medical conditions/system disorder
- Risk factors for gestational diabetes, preeclampsia, etc.
What are you looking for in an antenatal blood test?
- Blood group and antibody (e.g; Rh factor)
- Hb - looking for anemia, hemoglobinopathies; SC disease, thalessemias, CF, etc
- Infections; syphilis, HIV, Hep B, rubella; *only ones that can be treated, managed
What would you check for in an antenatal urinalysis?
- Proteins; the ratio of protein:creatinine can help diagnose preeclampsia
- Nitrates
Other than taking urinalysis, blood test and history what else would you do during antenatal screening?
Ultrasound to check fetal viability
How is the maternal CVS and blood affected during pregnancy?
Increased blood volume: since CO = SV X HR they all increase
What happens to the systemic vascular resistance and the BP?
Systemic vascular resistance decreases:
Progesterone causes vasodilation -> reduced afterload -> decreased BP/hypotension
But BP should return to normal during third trimester
How is the preload and afterload affected during pregnancy?
Preload increases, afterload decreases (due to reduced systemic vascular resistance)
What happens to the diaphragm during pregnancy? Which other structure does this affect?
Moves up due to the increased pressure from the uterus, this displaces the heart
When and why can aortocaval compression occur? What advice can be given to prevent consequences of this?
In the third trimester: Compression of the abdominal aorta and IVC due to the gravid uterus when a pregnant women lies on her back
-> lie on her L side since IVC is on the R side (so baby’s weight can’t put pressure on it and vessel remains open)
How do endothelia change in pregnancy?
- More permeable (hormones)
2. Progesterone causes vasodilation
Name six factors that put some women at risk for preeclampsia. When will signs of it begin to show?
Signs show after 20-21 weeks, but milder case = later diagnosis
- FH
- High BMI and first pregnancy
- Older women having their first pregnancy
- Multiple pregnancies
- Chronic hypertension
- Any autoimmune condition
What is preeclampsia, how is it caused and how is it managed?
*Also what is it characterized by?
Pregnancy complication as a result of widespread endothelial damage caused by an imbalance between androgenic and antiandrogenic factors. The trophoblast cells fail to invade into the spiral arteries; so the vessels remain thick and muscular and their is a reduction of blood flow reaching the baby, hindering the baby’s growth
Characterized by high blood pressure (rises when there is endothelial damage) and signs of damage to another organ system (e.g; kidneys, liver)
Only treatment option is to treat the BP, monitor the kidney/liver function and try to extend the pregnancy as long as you can until the mother begins to deteriorate (e.g; can’t control her BP) or there is risk of damage to fetal growth (latest 34 weeks)
How are the kidneys affected during pregnancy? (4 things)?
How does the volume that the urinary system has to deal with change?
Volume increases by 30%
- The GFR increases by 40-65%
- Renal plasma flow increases by 50-80%
- Filtration capacity remains intact
- Functional renal reserve (ability to increase the renal plasma flow and GFR) decreases because the GFR increases
What happens to the blood creatinine as GFR increases in pregnancy and what are the normal serum creatinine ranges in pregnancy? What does it mean if this value is abnormal?
Decreases, normal pregnancy ranges are between 25-75mmol/L, if this is abnormal can be a sign of preeclampsia or other renal pathologies that have been aggravated during pregnancy
What happens to the bladder and the ureters during pregnancy and why? What is one complication that can arise as a result
Due to the influence of progesterone…
- Bladder doubles its capacity (10000 mL) (relaxing influence of progesterone)
- Ureters dilate - this also predisposes to an ascending bacterial infection
What are some consequences that can happen in the urinary system as a result of pregnancy
Urinary stasis (progesterone effect): can lead to hydronephrosis (kidney swells due to urine failing to properly drain from kidney to bladder) and cause hydroureter.
Can also lead to obstruction and a UTI; which can causes pyelonephritis (inflammation of the kidney typically due to a bacterial infection) which can irritate the uterus putting women at risk of going into pre-term labor
When would you want to investigate a pregnant woman for a UTI? How would you diagnose an asymptomatic pregnant woman with one?
Investigate/offer renal scan when the woman experiences backache or flank pain and has dysuria
Many pregnant women with bacterial infections in the urine are asymptomatic so have to check nitrites in a urinalysis
What happens to the chest wall in pregnancy and why? What happens as a consequence of this?
The following increase; subcostal angle, chest wall circumference, chest wall anterior-posterior and transverse diameters
These changes compensate for the 4cm elevation of the diaphragm (due to the expanding uterus) so that the total lung capacity isn’t significantly reduced - however, there is still a reduction in the functional residual capacity
Define the following and describe how they change in pregnancy A) Vital capacity B) Total lung capacity C) Minute and alveolar ventilation D) Tidal volume E) Respiratory rate
A) Max exhalation after max inhalation; unchanged
B) Vital capacity + residual volume; unchanged
C) Amount of air expelled from alveoli/min; Increased
D) Volume of air moved in-out of lungs with each ventilation cycle; increased
E) Amount of breaths/min; unchanged
Name two physiological respiration issues pregnant women experience and why they occur.
Physiological hyperventilation occurs due to
- increased metabolic CO2 production
- progesterone also stimulates a respiratory drive causing the woman to hyperventilate
Physiological dyspnea; due to progesterone driven hyperventilation
What is a consequence of physiological hyperventilation and how is it compensated for?
This causes respiratory alkalosis which is compensated for by increased renal bicarbonate excretion
What happens to the PaO2, PaCO2 and FEV1 in pregnant women?
PaO2; increases
PaCO2; decreases
FEV1; unchanged
Why does the vital capacity remain the same in pregnancy?
The expiratory reserve volume reduces in pregnancy but to compensate the tidal volume and the inspiratory reserve volume increase
What happens to the mothers insulin resistance as the pregnancy progresses and why?
Maternal peripheral insulin resistance increases and her body switches to gluconeogenesis and alternative fuels (so more glucose goes to the baby)
This is achieved by anti-insulin hormones that are increased in pregnancy; hPL, prolactin, estrogen/progesterone, and cortisol