Pregnancy Flashcards
What is the role of progesterone in pregnancy
-Progesterone is directly synthesised from cholesterol
- decidualisation
- smooth muscle relaxation- prevents the uterus from contracting
- mineralocorticoid changes- water retention- cardiovascular changes
What is the role of oestrogen in pregnancy
- The placenta lacks the enzymes 17-a hydroxylase and 17 lyase, thus the fetal adrenal gland synthesises oestrogen in an alternative pathway
- uterine hypertrophy
- Metabolic changes: insulin resistance
-increasing clotting factor production (haemostasis)
-breast development
How much weight is gained throughout pregnancy
At 20 weeks: 9-13kg during the pregnancy
- foetus and placenta
- breasts
-uterus
-fat and proteins
-Body water
How is basal metabolic rate affected by pregnancy
BMR is the energy required to sustain basic functions at rest
in pregnancy the basal metabolic rate increases as the growing foetus and the placenta require energy for their development
- increased levels of glucose in the maternal circulation
How are levels of glucose increased during pregnancy
In the first trimester: pancreatic cells increase in their number - increase levels of insulin so more glucose is taken up into tissue.
- fasting serum glucose decreases
In the second trimester: Placental lactogen causes insulin resistance. less glucose is taken into stores and there is an increase in the serum glucose levels
- glucose is transported across the placenta as a foetal energy source.
foetus stores glucose in the liver
How do oestrogen and progesterone result in a total water gain
Estrogen and progesterone are so high that they act like mineralocorticoid….retain more sodium from kidneys thereby increasing blood volume.
RAAS - placental renin production. Estrogen upregulates angiotensinogen synthesis by liver leading to increased angiotensin II and aldosterone. Despite higher ANGII women resistant to AT2 receptor mediated vasoconstriction because progesterone decreases vasosensitivity.
Connective tissue and ligaments take on water and become a bit softer.
Resetting osmostat, decreased thirst threshold. Decrease in oncotic pressure (albumin).
How does estrogen and progestrone effect respiration
Estorgen and progesterone:
The respiratory centre becomes more sensitive to CO2 and
the anatomical changes- ribcage moves upwards and flare outwards which cause you preganant women to breathe more deeply.
This causes an increase in the arterial partial pressure of oxygen and decrease in the partial pressure of CO2
this facilitates gas transfer so their is increased O2 transfer from the mother to the foetus.
decreased maternal pCO2 allows for CO2 to move from the foetus to the mother
What are the changes in maternal blood during pregnancy
-There is an increase in the plasma volume
- There is an increase in red cell mass
(This allows for increased iron absorption from the gut)
However a much greater increase in plasma volume than the red cell mass, this results in haemodilution and may appear as anaemia.
There is increased white cells and blood becomes hypercoaguble. Increased fibrinolysis - for placental seperation but their is increased risk of thrombosis.
What are the effects on the cardiovascular system
Pregnancy is characterised by a low pressure, high blood volume system.
- Expanding uterus -
-pushes the heart
- altered ECG and heart sounds - Inc. Vasodilation by steroids
- estrogen causes increased levels of NO which causes smooth muscle vasodilation
- Inc vasodilation causes decreases TPR which increases cardiac output,
- Inc blood to skin, kidney, muscle, placenta and uterus. - Increased Cardiac output by steroids
increased heart rate - Neoangiogeneis: extra cappilaries in the skin which assist heat loss
What are the effects of steriods on the GI tract
- Increased thirst and appetite
- Decreased GI motility — constipation
- Relaxed oesophegal sphinter —- acid reflux
What dietry supplementation is necesary for pregnant women
FOLIC ACID
DNA synthesis
growth of blood vessels
aid the developing uterus, foetus and placenta
400ug a day
ideally 3 months before pregnancy
deficiency leads to spina bifidia and neural tube defects
How is the urinary system affected in pregnancy
- Inc blood flow to the kidney, inc filtration rate, inc clearance of creatanine, uric acid, reduced glucose reabsorbtion rate
- The placenta produces relaxin, this favours endothelial cell formation and causes NO release causes vasodilation of the renal arteries.
inc risk of UTI - Progesterone and VEGF cause dec sensitivity to Angiotenisn II- this reduces angiotensin II mediated vasoconstriction and increased blood flow to the renal arteries and increased filtration
- Increased frequency: Increased pressure of growing uterus on bladder
How is the foetal HPA axis affected
Hyp—- CRH
Pit—– ACTH
Adrenal—– cortisol (positive feedback)
The placental CRH stimulates the HPA axis to produce high levels of cortisol and DHEA.
Cortisol effects:
- Metabolic effects:Insulin resistance
-Mineralocorticoid actions
- Foetal lung maturity
- Inc. prostaglandins
-Placenta produces- oxytocin and estrogen
DHEA effects:
DHEA is aromatised into estrogen
Inc Estrogen: progesterone ratio
prostaglandin secretion: uterine contractions, activates blood flow and cervical ripening
What are the changes to the thyroid gland
Thyroid hormone regulated the rate at which cells use oxygen to produce energy.
Increased thyroid hormone levels to meet the metabolic demands of pregnancy.
Increased risk for gestational thyrotoxicosis: HCG may act on TSH receptor (overactive thyroid gland)
biochemical test may indicate pregnant women to have hyperthyroidism
side effects: anxiety, tremor, heat intolerance, weight loss
How does the cervix change during pregnancy
the function of the cervix is to retain the pregnancy
- Increases in vascularity
The tissue softens from 8 weeks
- changes in connective tissue
- prepares for expansion
- Proliferation of glands
great increase in mucous production
anti-infective
