fetal and maternal adaptations in pregnancy Flashcards
how does the body prepare in the menstrual cycle for pregnancy?
peripheral vasodilation and resultant haemodynamic changes occur during each luteal phase
what facilities maternal adaptations?
2-way communications between maternal and fetal tissues
pregnancy hormones - oestrogen, progesterone, HCG, prolactin, oxytocin, relaxin
subsequent effects on maternal endocrinology
what is hCG produced by?
syncytiotrophoblasts
- marked rise in first trimester then declines
maintains crops luteum
what does progesterone do?
increases until just before labour pro-gestational = smooth muscle relaxation, inhibits OTR expression, increases maternal ventilation proves glucose deposition in fat stores raises body temp
what does oestrogen do?
produced by CL and then placenta increases until just before labour promotes CV changes insulin resistance breast and nipple growth uterine blood flow and myometrial growth carvical softening increases OTR expression in myometrium water retention
what hormone increases throughout pregnancy and promotes insulin resistance, lactogenic?
human chorionic sommatomammotropin - produced by syncytiotrophoblasts
what does placental CRH do?
increases throughout pregnancy
plays role in parturition
what does prolactin do?
milk production
what does oxytocin do?
milk ejection reflex
contraction of smooth muscle of uterus and PG production
what does relaxin do?
secreted by corpus luteum, decidua, placenta
remodelling of connective tissue - pelvic gurdle pain
why do hormonal changes occur in pregnancy?
supply nutrients to fetus
support amniotic fluid production
clear fetal waste products
meet fetala nd placental demands for glucose, aa and oxygen
adapt in prep for labour - protect mum from CV insults at delivery
what happens to the uterus during pregnancy?
10 fold increase in weight and blood Flow
size changes from pear shaped to thin walled spherical structure
composition is muscle cell hypertrophy, increased elastic tissue and fibrous tissue
hypertrophy of uterine and ovarian vessels
orientation straightened ad dextrorotates with increase size
what happens to the cervix in pregnancy?
increases vascularity and oedema, softening,
increase cervical glands -> production of tenacious mucous plug
hyperplasia/eversion of endocervical epithelium
what happens to the vaginal during pregnancy?
venous congestion -> blue/purple tint
oestrogen increases glycogen deposition in epithelium -> increase lactic acid
what changes occur in the breast in pregnancy?
lactiferous ducts and alveoli proliferate
increase in size
skin changes
colostrum produced from 16wks
lactation when sudden decrease in oestrogen and progesterone and increase prolactin
suckling increases oxytocin = milk ejection
what are cardiovascular changes in pregnancy?
HR - increases up to 20% by 3rd trimester
Stroke volume - increases
CO - increases very early in 1st trimester, plates at 32wks then increases again at start of labour
total peripheral resistance (systemic valsuclar resistance) - falls
BP - falls until 24wks then slowly recovers to normal values at term
plasma volume - increases
how does the CV changes occur?
smooth muscle relaxation = vasodilation, fall in TPR, decrease after load, therefore perceived underfilling which triggers RAAS and causes increase in plasma volume >50%
increase HR and SV = increase CO
marked vasodilation causes BP to fall despite CO increase
how does pregnancy change the RAAS?
increase renin, increase angiotensin I and aldosterone so increases retention of water = increase fluid volume
what cardiovascular diseases cause problems?
valve disease = fixed CO, can push woman into L heart failure
pulmonary hypertension = can push them into R heart failure
connective tissue disease (marinas) = worry about aortic dissection and blood tracking and occluding - especially during pushing
cardiomyopathies
IHD
why should pregnancy women not lie flat?
can reduce CO - 30-50%
reduces uteroplacental perfusion - causes fetal distress
how much does uterine blood flow increase by?
50ml to 500-800ml/minute
blood loss can accumulate rapidly in PPH
(circulating volume only 5000ml)
what happens during labour to CO and why?
increases as the uterus contracts with each contraction giving a bolus of fluid into the maternal circulation each time
at what stage of labour does CO increase the most?
third stage - 80%
2nd stage - 45%
1st stage - 30%
latent stage - 15%
what are respiratory adaptations in pregnancy?
patients with lung disease do better than CVD patients
oxygen requirements increase by 16%
increase tidal volume and ventilation 30-40%
decrease in pCO2
trigger is unknown - may be progesterone effect - may trigger ventilation at lower pCO2
TLC - decreases 5%
residual volume and functional residual volume decreases due to diaphragm raising
no change to RR
what mechanical changes occur in response in pregnancy?
uterus expands, lower ribs flare diameter of chest increases thus diaphragm raised by 5cm chest wall compliance decreases
why is responsible adaptations important for anaesthetists?
can be difficult to intubate/ventilate due to oedema, breasts, fetus
pre-oxygenation for 3 minutes! buys time
what are the haematological adaptations of pregnancy?
blood volume expands 45%
fluid redistribution = increased plans and interstitial volume
RC mass increases due to erythropoiesis, iron requirements go up
plasma volume increases in greater than RC = dilution anaemia of pregnancy
WCC rise (neutrophils)
T and B cell decreases = increased susceptibility to some infections
platelets unchanged
what is an important haematological factor to identify that can cause maternal death?
hyper-coagulable state
pro-coagulators clotting factors increase
antithrombin falls
highest risk in post natal period
VTE is one of the commonest causes of maternal death
what are the structural renal adaptations in pregnancy?
increase in blood flow and size
increase progesterone = increase size of pelvis/collecting system
compression of pelvic brim = physiological hydronephrosis
overall effect = mild obstruction/urinary stasis = infection risk (can cause preterm labour or infections)
what are the functional renal adaptations of pregnancy?
increased blood flow rate
increased glomerular filtration rate
glycosuria is common
resistance to angiotensin II develops and RAAS generally activated - large increase in extracellular water and sodium
what are the GI adaptations in pregnancy?
relaxed lower oesophageal sphincter and pressure from uterus = reflux and decreased gastric motility
gall bladder increases in sized empties slower - degree of cholestasis
pathological = obstetric cholestasis (still birth risk factor) pancreatitis risk factor
progressive insulin resistance during 3rd trimester of pregnancy, increase glucose circulating levels
lipids increase = can’t interpret bloods in pregnancy (cholesterol)
