L9 Adaptation to Pregnancy Flashcards
Outline the 3 key hormonal changes during pregnancy:
- hCG: initial peak from 4 to 12 weeks then gradual decline
- Progesterone: Dominant and gradually increasing before tapering after 36 weeks (peaks in 3rd trimester)
- Oestrogen, gradual rise, become dominant ~24 weeks and rises more rapidly
What are the sources of progesterone during pregnancy:
- Initially: corpus luteum
- Placenta takes over as dominant source by week 12
How do hormonal changes during pregnancy impact the gallbladder?
- Progesterone reduces contractility (acting as a smooth muscle relaxant)
- Oestrogen increase results in higher cholesterol concentration in the bile -> slower bile flow -> more chance of precipitation
- Increased risk of gallstones during pregnancy
- This process is hastened by dehydration (e.g. after vomiting)
What are the sources of oestrogen during pregnancy?
- As with progesterone, initially released by corpus luteum
- At 9 weeks, placenta takes over
- Synthesis peaks in 3rd trimester
What is thought to be the major function of hCG during pregnancy?
- Rapid exponential rise peaking at 9 - 10 weeks
- Thought to be maintaining the corpus luteum
- This ensures adequate progesterone production in early stage of pregnancy before placenta steps in
- Also has a role in regulating oestrogen production
- Role in regulating maternal blood supply
What general roles does oxytocin play in pregnancy and labour?
- Supporting prolactin in milk production -> act to stimulate milk ejection
- Analgesic/amnesic effect during labour
- Other psychological effects (mother-infant bonding)
- Key role: Inducing labour (3 - 4x increase during labour) -> stimulates contraction of myometrium -> PG release -> further contraction stimulus
- Feedback loop with posterior pituitary upon activation of cervical sensory receptors by baby’s head -> further oxytocin release
What effects does pregnancy have on the brain?
- Reduces brain size (loss of grey matter)
- Increased neuroplasticity similar to that of adolescence -> preparation for taking on new skills/experience during child rearing
- Associated with adaptations in various brain regions to support caregiving/maternal instincts
- Neuroplasticity may also associated with risk of post-partum depression
Outline the role of progestins during pregnancy:
- Progestational effects…
- Smooth muscle relaxation (including peripheral vasodilation)
- Inhibition of oxytocin receptor expression
Outline the role of oestrogens during pregnancy:
- Breast, nipple growth (anabolic)
- Uterine blood flow, myometrial growth
- Promotes changes in CV system
What is the role of prolactin in pregnancy?
- Milk production
- Increases throughout pregnancy
- Milk released upon oxytocin stimulation
Give 2 examples of changes to skin during pregnancy:
- Hyperpigmentation (e.g. linea nigra, facilitated by increased melatonin)
- Striae gravidarum/stretch marks (usually dissipate after birth)
Changes to mammary glands during pregnancy:
- Breasts: Increased size and sensitivity
- Darkened areolas (melatonin increase)
- Colostrum production
What are the 4 major haematological changes during pregnancy?
- Increased plasma volume
- Increased total blood volume
- Increased red cell mass -> But decreased overall concentration; can lead to anaemia due to increased plasma volume
- Increased white cell count (WCC)
Benefits and risks of increased coagulation during pregnancy:
- Useful in preventing PPH
- Increased risk of venous thromboembolism
How long does hypercoagulation last following pregnancy?
- Persists for first 3 weeks after delivery
- Resolves by 6 - 8 weeks postpartum
What respiratory changes take place during pregnancy?
- Elevated diaphragm -> slightly decreased volume
- Key: Increased oxygen consumption (+30 - 50ml/min)
- Progesterone muscle relaxant effect -> increased tidal (i.e. resting) volume without increased respiratory rate
How do gas exchange and pH change during pregnancy and why?
- Increased pH and paCO2 -> fetal Hb has better affinity than adult Hb -> makes oxygen more available for fetus
- Excretion of HCO3 through kidneys facilitates this (basic)
What anatomical changes does pregnancy exert on the cardiovascular system?
- Elevated diaphragm -> heart displaces up and left
- Apex moves laterally -> ECG altered
- Increased ventricular muscle mass (greater stroke volume)
- Increased size of left ventricle adn atrium
Outline the physiological changes that occur in the cardiac system during pregnancy:
- Increased cardiac output (+40%)
- Increased stroke volume (+30%)
- Increased HR (+10-15%)
- Reduced blood pressure and peripheral resistance (relaxant effect of progesterone)
2 key symptoms of pre-eclampsia:
- Increased BP (conversely, pregnant women usually have lowered BP compared to normal)
- Ketonuria/protein in urine
Outline the changes to gastrointestinal tract during pregnancy:
- Progesterone -> relaxed lining of tract, slower movement through bowel
- This allows increased absorption of water and nutrients
- However, it does also make constipation common in pregnant women
- Also see relaxation of oesophageal sphincter, leading to heartburn where stomach acid is permitted to rise up oesophagus
How is the bladder affected during pregnancy?
- Progesterone -> affects ureters, results in enlarged kidneys (hydronephrosis), increased size of ureters (hydroureter)
- Larger bloodflow -> increased GFR -> increased urinary output
- Slower progress through ureter -> risk of UTI, can travel up to kidneys leading to pyelonephritis
What factors make pyelonepritis a potential complication in 1 - 2% of pregnancies?
- Decreased ureteral peristalsis
- Lowered detrusor tone
- Less mechanical compression of ureters and incomplete bladder emptying
- Overall: Risk of infection to kidneys
Why is proteinuria common in pregnancy and when does it become pathological?
- Increased reabsorption of solutes through renal tubules
- Results in tendency towards proteinuria (+1 normal)
- Higher value indicative of preeclampsia
Changes in uterus during pregnancy:
- Uterus: Initially pear shaped with ~10ml volume, increased to spherical then oval structure with max 5l volume due to smooth muscle hyperplasia and hypertrophy
- Also see increase in elastic tissue and supportive fibrous tissue, with
over 10x increase in blood flow by full term - There is a slight drop in height of fundus at 40 weeks when baby’s head repositions ready for delivery, which relieves some of the congestion
How is the cervix affected during pregnancy?
- Increased vascularity
- Oedema (swelling due to fluid) -> softening
- Greater cervical glands, production of mucous plug
- Hyperplasia/eversion of endocervical epithelium
What does aortocaval compression cause?
- Baby causes aortocaval compression (pressure when lying down -> venous collapse)
- Oedema
- Raised risk of VTE
What are some of the key changes that are checked postpartum?
- Involution of the uterus to original size and shape (initially rapid, but full reversion takes up to 6 weeks)
- Cervical changes return to normal
- Lactation
- Perineal health (pelvic floor exercises)
- Mental health (PP depression etc)
What is Vichow’s triad?
- Increased coagulation factors
- Decreased fibrinolysis
- Venous stasis
