Lecture 17- Maternal physiology and pregnancy Flashcards
Why does the body need to adapt
x
To allow the foetus to grow
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Volume support
- Volume expansion
- Vasodilation
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Nutrition
- Increased respiration
- Insulin resistance
- Increased absorption
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Waste clearance
- Increased GFR
- Hepatocellular stimulation
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Pregnancy maintenance
- Uterine quiescence
- Immunologic sequestration
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Childbirth
- MSK
- Clotting
what drives maternal adaptations
hormones etc
- hCG
- oestrogen
- progesterone
- relaxin
- softens ligaments and widens the cervix
changes in immunity
the foetus is genetically different (hemi-allograft)
- will be recognised by the maternal immune system if the mother does not become immunosuppressed
–> allo-response is not cytotoxic
Pregnancy= immunosuppressed state therefore
- Higher attack rate and severity of certain viral pathogens i.e. varicella, flu etc
- May improve certain autoimmune conditions
immune changes
Reduced Th1 (cytotoxic) and increased Th2 (more regulatory)
changes in respiration
- increased inute ventilation (Increased tidal voluem and respiratory rate
- decrease paCO2
- increased paO2
- pH changes
- decreased functional residual capacity
anatomical changes in respiratory system
growth of the foetus during pregnancy causes upward displacement of the diaphragm.
However, this does not decrease the total lung capacity significantly as there is also an increase in the transverse and anterior-posterior diameters of the thorax.
In pregnancy a woman faces an increase in their metabolic rate, which leads to an increased demand for oxygen. how does the body adapt to help the mother meet the oxygen demand?
The tidal volume and the minute ventilation rate increases
Many women experience hyperventilation during pregnancy, it is thought that the reason for this is the increased carbon dioxide production and the increased respiratory drive caused by
progesterone.
This hyperventilation results in a respiratory alkalosis with a compensated increase in renal bicarbonate excretion.
need to still consider pathological causes and excerbating factors of dyspnea
- cardiac
- anaemia
- DVT/PE
- Asthma
- Pneumonia/ARDS (acute resp distress syndrome)
- PE
changes in cardiovascualr system
- Increased SV (early pregnancy)
- Increased HR (late pregnancy)
- Increased cardiac output (CO= SV x HR)
blood pressure and pregnancy
As discussed above, during pregnancy progesterone levels increases. Progesterone acts to decrease systemic vascular resistance in pregnancy which leads to a decrease in diastolic blood pressure during the first and second trimester of pregnancy.
In response to this the cardiac output increases by about 30-50%. An increase in blood pressure in pregnancy could be an indication of pre-eclapmsia.
why does the total blood volume increase during pregnancy
Pregnancy (progesterone and ostrogen) results in the activation of the renin-angiotensin-aldosterone system, leading to an increase in sodium levels and water retention. This means that the total blood volume increases= Increased stroke volume
- release of renin from kidneys
- angiotensiongen from the liver
consequences within the cardiovascular system
- icnreased RAAS- peripheraledema
- chganges in plasma volume >>>> change in RBC volume –> dilutional anaemia
- clotting - hypercoagylabvle state = increased number of thromboembolic events
clotting during pregnancy
- Increased procoagulants (eg. Fibrinogen, factor VIII, vWF)
- Decreased anticoagulants e.g. protein S
- Reduced fibrinolysis
changes in the renal system
Increased cardiac output and systemic vasodilation during pregnancy causes an increase in renal plasma flow
- Which increases the GFR by about 50-60%.
- This would mean that there is an increase in renal excretion, so in pregnancy the plasma levels of urea and creatinine will be lower.
- decreased PCT absorption
decreased PCT absorption=
glucosuria–> not enough time for reabsorption
structural changes in the urinary system
- Progesterone affects the urinary collecting system causing relaxation of the ureter (resulting in hydroureter) and relaxation of the muscles of the bladder.
- Both of these changes causes urinary stasis which predisposes a woman to UTIs, commonly pyelonephritis.
smooth muscle relaxation of ureters and bladder muscle cause
decreased speed of urine passage
e..g if goe son for a while back log of urine = hydronephrosis
Changes in the GI system: anatomical
The growth of the uterus causes a number of anatomical changes related to the gastrointestinal tract. One of these is the upward displacement of the stomach as the uterus grows, this leads to an increase in intra-gastric pressure which would predispose the mother to gastrointestinal reflux, along with symptoms such as nausea and vomitng.
Changes in the GI system: due to progesterone
Slow transit time= increases the time in which to absorbed water, vitamins and nutrients
slow transit time canc ause
constipation acid reflux
changes in LFT (liver function tests) during pregnanct
- ALP levels increased due to placental synthesis
Increased progesterone also causes relaxation of the gallbladder so
so biliary tract stasis may occur. This predisposes the mother to getting gallstones.
changes in the endocrine system: oestrogen and progesterone
Throughout pregnancy the levels of progesterone and oestrogen increase; the oestrogen being produced by the placenta and the progesterone being produced by the corpus luteum and later by the placenta.
changes in the endocrine system: adaptations of the thyroid
- Increase in oestrogen levels results in an increase in hepatic production of thyroid binding globulin (TBG).
- As a result, more free T3 and T4 bind to the TBG, this causes more thyroid stimulating hormone to be released from the anterior pituitary gland (due to inhibited negative feedback).
- Therefore, the free T3 and T4 levels remain unchanged – but the total T3 and T4 levels rise.
Thyroxin
is essential for the foetus’ neural development, but the foetal thyroid gland is not functional until the second trimester of gestation (8-12 weeks).
Hence, increasing T3 and T4 levels in the mother ensures that there is a constant supply of thryoxin to the foetus early in pregnancy.
changes in the endocrine system: adaptations in PTH and calcium
- Calcium for the growth of the babies bones used up
- Stimulation of Parathyroid
- Causes increase in PTH
- Increase 25(OH) D
- Increase alpha hydroxylase which activates 25(OH) D to vitamin D increases Ca and phosphorus absorption
- Mother needs to eat food rich in calcium
during preganacy there is also an increase in which hormones
- human placental lactogen
- prolactin
- cortisol levels.
These are anti-insulin hormones therefore, they increase insulin resistance in the mother and reduce peripheral uptake of glucose. This ensures that there is a continuous supply of glucose for the foetus.
Changes in the endocrine system: glucose metabolism
- Increase in glucose levels
- Increase in glucose which enhances fetal growth
- Pregnancy is a diabetogenic situation
- Insulin resistance
- Increased insulin secretion
having impaired glucose metabolism e.g. diabetes, before pregnancy
will increase insulin resistance
- More glucose passes foetal barrier (insulin cannot pass)
- Increase in production of insulin
- Increases substances for fetal growth
- Enhanced foetal growth–> gestational diabetes
gestational diabetes
- onset of elevated blood sugar levels during pregnancy and falls under the umbrella term hyperglycaemia (includes T1 and T2)
consequence of gestational diabetes
- Usually resolves after birth
- Increased risk of DM later in life
- Pregnancy determinants of insulin resistant
- Ethnicity
- Physical inactivity
- Obesity
- Dietary composition
- PCOS
gestational diabetes issue for baby
macrosomnia
The term “fetal macrosomia” is used to describe a newborn who’s much larger than average.
Labor problems. Fetal macrosomia can cause a baby to become wedged in the birth canal (shoulder dystocia), sustain birth injuries, or require the use of forceps or a vacuum device during delivery (operative vaginal delivery)
gestational dibates issue for mums
instrument and operation delivery interventions trauma
changes in MSK and skin: MSK
- Back pain, shoulder pain, tension headaches
- Change in centre of gravity
- Increased lordosis and kyphosis
- Forward flexion of neck
- Stretching of abdominal muscles
- Impede posture
- Strain paraspinal muscles
- Change in centre of gravity
- Pelvic pain
- Increased mobility of sacroiliac joints and pubic symphysis
- Anterior tilt of pelvis
- Fluid retention can cause compression structures such as median nerve (carpal tunnel)
Adaptations in skin
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- Chloasma – mask of pregnancy
- Palmar erythema
- Vascular spides
- Linea nigra
pre-eclampsia
- Hypertension and proteinuria
pre-eclampsia usually presents in
the third trimester and resolves after delivery (can occur postpartum)
risk factors of pre-eclampsia
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Risk factors
- Chronic and gestational HTN
- Pre-existing renal disease
- Diabetes
- Obesity
- Family history
- First pregnancy
- Extremes of age
- Pre-eclampsia in prior pregnancy
- Multiple gestation
- IVF
Pathogenesis of pre-eclampsia
Pathogenesis
- Impaired invasion of trophoblast leading to shallow invasion of spiral arteries
- Remain small calibre and of high resistance
- Leads to hypoperfusion and ischaemia
- Systemic endothelial dysfunction in maternal system
- Begin to see hypertension due to vasoconstriction
- Systemic endothelial dysfunction in maternal system
Signs and symptoms of preeclampsia: mild
- elevated blood pressure
- elevated protein in urine
- weight gain
- water retention and swelling
Signs and symptoms of preeclampsia: severe
- headaches
- changes in vision
- nausea and vomiting
- pain in abdomen and back
Complications of preeclampsia
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Maternal
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- Seizures (high bp due to vasoconstriction due to endothelial dysfunction)
- Cerebral haemorrhage
- Renal failure
- PE
- DIC and thrombocytopenia
- Hepatic failure or rupture
Complications of preeclampsia
- Fetal
- Growth restriction
- Oligohydramnios
- Placental infarcts or abruption
- Fetal distress
- Premature delivery
- Stillbirth
summary of maternal adaptations in pregnancy
