Maternal physiological adaptations to pregnancy Flashcards
What are the pregnancy hormones
Progesterone Oestrogen Placental prolactin Placental lactogens Corticotropin-releasing hormone (CRH) Aldosterone EPO
What produces progesterone in pregnancy
Corpus lute and then placenta
What produces oestrogen in pregnancy
Placenta and fetes
How does fetus protect itself from secreted hormones
Placental polarity/barrier
Fetus can conjugate steroids to sulphates making them biologically inactive
What does placental prolactin do
Breast chances, behavioural changes
What do placental lactogens do
For maternal insulin and glucose metabolism, lipolysis, EPO
What does cirticotropin releasing hormone do
- where is it released from
- What are the risks of increased levels
Leads to increased secretion of cortisol from mother- its a stress response
Released from placenta
Increased levels can affect nutrient transfer and the placental clock. Risks can be pre-term labour, early parturition signals
What does aldosterone affect
Plasma volume
What does EPO affect
Red blood cells
What cytokines are released in pregnancy
Pro-inflammatory interleukins, TGF-beta
What vasodilatory mediators are released in pregnancy and use
VEGF, NO (for vasodilation and angiogenesis)
how does uterus change in pregnancy
Expands and increases in weight
How does uterine musculature change in pregnancy
Hypertrophy. Needed for expulsion of fetus at parturition
What happens to heart during pregnancy
Apex of heart moved to anterior and to the left (pushed up and rotated forwards)
Left ventricular hypertrophy to cope with increased maternal cardiac output
What happens to calcium concentrations in pregnancy
Increased intestinal calcium absorption, maternal bone loss may occur in last trimester and lactation. Reversible
What happens to blood volume in pregnancy and how does this occur
Increase (over 40%)
Stimulation of RAAs- aldosterone leads to increased sodium and water retention so increased plasma volume
What happens to red cell mass during pregnancy and why
Increases linearly
Increased renal EPO increases red cell mass
What happens to hematocrit and haemoglobin during pregnancy and why
advantage of this
Fall. Because plasma volume increases more than cell mass
Advantage- decreased viscosity leads to reduced resistance in flow so better placental perfusion
What happens to haemoglobin during pregnancy and why is this beneficial
50% higher. Useful protection against any blood loss at delivery
What will help restore haemoglobin levels in pregnant women
Iron and folic acid
What relaxes smooth muscle cells of arteries
VEGF
PLGF
NO
Progesterone
What do angiogenic, permeability and vasoactive factors do to vasculature
What is the consequence of this
Vascular dilatation and relaxation of peripheral vascular tone
Establishment of the new vascular beds, including the utero-placental circulation
Lowers blood pressure (contributes to increased blood volume)
-Reduction in peripheral vascular resistance which reduces by about 40% in mid pregnancy, rising slowly to term
What happens to stroke volume in pregnancy and why
Increase
-Because of increase in blood volume which means more blood enters heart (preload) and decrease in peripheral resistance due to vasodilation leads to reduced after load
What happens to maternal heart rate in pregnancy
Increase
What happens to cardiac output during pregnancy and why is this needed
Increase
-AN extra 30-50ml of oxygen is consumed per minute during pregnancy
What can happen to women with valvular heart disease during pregnancy and why
Pulmonary oedema
Have difficulty accommodating raised CO
What is systolic and diastolic bp like during pregnancy
Systolic- remains stable
Diastolic- early, falls and reaches plateau at around 20 weeks and rises to normal values by term
IN mid-pregnancy what can happen if a woman lays supine
Enlarging uterus compresses both the inferior vena cava and the abdominal aorta.
Vena Cana: This reduces venous return to the heart so fall in pre-load and cardiac output. Resultant fall in BP may be severe enough for the mother to lose consciousness
Aorta: reduction in uteroplacental and renal blood flow. During last trimester, maternal kidney function is markedly lower in the supine than in the lateral position
What is maternal oxygen consumption like to all tissues throughout pregnancy
Increased
What are the structural changes in the respiratory system to accommodate for increased o2 consumption
Increased chest expansion, displaced diaphragm, increased vascularisation of upper respiratory tract
What are the ventilatory changes in the respiratory system to accommodate for increased o2 consumption
Progesterone-mediated hypersensitivity to CO2 increases the respiratory rate
Tidal volume increases
Alveolar ventilation is higher
Therefore there is a fall in arterial and alveolar CO2 tensions. PaO2 increases
What is the consequence of a fall in arterial and alveolar CO2 tensions and an increase in PaO2 to the baby
The higher PaO2 on the maternal side of the placenta facilitates oxygen transfer to fetus, whilst the lower PaCO2 facilitates transfer of CO2 in the reverse side
Anatomical changes to maternal kidneys
Kidneys enlarge due to increased vasculature, vascular dilatation and interstitial space increases
Renal parenchymal volumes increase in pregnancy, glomerular diameters are greater
Dilatation of the calyces, renal pelvis and ureter. Increased chances of urinary tract infection
Bladder loses tone: increased urinary frequency, urgency
Physiological changes to renal function
Increase in renal plasma flow, decrease in renal vascular resistance
Changes in GFR and glomerular filtration fraction
Changes in tubular re-absorption
What happens to filtration fraction in early pregnancy
Declines in early pregnancy
Formula for amount of glucose in urine
Amount of glucose filtered through the glomerulus minus the amount reabsorbed by the proximal tubules
What may be present in a pregnant woman’s urine
What is a consequence of this
Glucose (glycosuria) because filtered load of glucose rises in pregnancy and exceeds maximal rate of reabsorption.
Increases chances of UTI
Where does fetus get its glucose from
Mother
What happens to glucose levels in mother during pregnancy
Fasting hypoglycaemia in first trimester, the decrease in glucose levels reach their plateau about 12 weeks gestation. Then it reverts to normal in second and third trimester
What do progesterone and insulin do
Progesterone increases maternal appetite and stimulates deposition of glucose in fat stores
Increase in insulin secretion favours lipogenesis and storage of fat
What is absorption like mid pregnancy onwards
Increased absorption
What is gluconeogeneis like mid pregnancy onwards
Increased
What happens to free fatty acids and lipolysis from mid pregnancy onwards
Mobilised
What does enhanced lipolysis mean
Increases free fatty acid oxidation and ketones. It is an alternative fuel and can be used by mother so reduces her need for glucose which can be spared for fetus
After 20 weeks of pregnancy, what happens to plasma glucose levels
Revert to normal
What is the duration of postprandial hyperglycaemia in pregnancy
Prolonged
What is postprandial hyperinsulinimea
During last trimester:
- Higher glucose peak leads to higher insulin secretion
- Insulin reaches its peak after 1h
- Declines slowly but not back to basal levels in pregnancy
When is insulin resistance higher
Gestational diabetes and maternal obesity
How does fetus avoid maternal rejection
Placenta is a structural barrier stopping direct contact of maternal blood with fetus
Syncytial structure of the syncytiotrophoblast means maternal immune cells cannot cross to the fetus without going through the cytoplasm and being degraded. If they do manage to transcytose to the placental storm, fetal macrophages will phagocytose maternal immune cells
Which immune cells present in endometrium
Dendritic cells (APC)
Helper T cells
T regulatory cells
Uterine natural killer cells
What happens to T helper cells under the influence of pregnancy hormones
Decline relative to the suppressor cells or T regulatory cells in the endometrium (these decrease immune function so maintain materno-fetal tolerance)
What can be used to suppress immune reactions
Extra- villous trophoblast cells
What may soluble factors provide
Local immunoprotection of the fetus
