fetal and maternal adaptations in pregnancy

Question 1

how does the body prepare in the menstrual cycle for pregnancy?

Answer 1

peripheral vasodilation and resultant haemodynamic changes occur during each luteal phase

Question 2

what facilities maternal adaptations?

Answer 2

2-way communications between maternal and fetal tissues
pregnancy hormones - oestrogen, progesterone, HCG, prolactin, oxytocin, relaxin
subsequent effects on maternal endocrinology

Question 3

what is hCG produced by?

Answer 3

syncytiotrophoblasts
- marked rise in first trimester then declines
maintains crops luteum

Question 4

what does progesterone do?

Answer 4

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

Question 5

what does oestrogen do?

Answer 5

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

Question 6

what hormone increases throughout pregnancy and promotes insulin resistance, lactogenic?

Answer 6

human chorionic sommatomammotropin - produced by syncytiotrophoblasts

Question 7

what does placental CRH do?

Answer 7

increases throughout pregnancy

plays role in parturition

Question 8

what does prolactin do?

Answer 8

milk production

Question 9

what does oxytocin do?

Answer 9

milk ejection reflex

contraction of smooth muscle of uterus and PG production

Question 10

what does relaxin do?

Answer 10

secreted by corpus luteum, decidua, placenta

remodelling of connective tissue - pelvic gurdle pain

Question 11

why do hormonal changes occur in pregnancy?

Answer 11

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

Question 12

what happens to the uterus during pregnancy?

Answer 12

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

Question 13

what happens to the cervix in pregnancy?

Answer 13

increases vascularity and oedema, softening,
increase cervical glands -> production of tenacious mucous plug
hyperplasia/eversion of endocervical epithelium

Question 14

what happens to the vaginal during pregnancy?

Answer 14

venous congestion -> blue/purple tint

oestrogen increases glycogen deposition in epithelium -> increase lactic acid

Question 15

what changes occur in the breast in pregnancy?

Answer 15

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

Question 16

what are cardiovascular changes in pregnancy?

Answer 16

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

Question 17

how does the CV changes occur?

Answer 17

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

Question 18

how does pregnancy change the RAAS?

Answer 18

increase renin, increase angiotensin I and aldosterone so increases retention of water = increase fluid volume

Question 19

what cardiovascular diseases cause problems?

Answer 19

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

Question 20

why should pregnancy women not lie flat?

Answer 20

can reduce CO - 30-50%

reduces uteroplacental perfusion - causes fetal distress

Question 21

how much does uterine blood flow increase by?

Answer 21

50ml to 500-800ml/minute
blood loss can accumulate rapidly in PPH
(circulating volume only 5000ml)

Question 22

what happens during labour to CO and why?

Answer 22

increases as the uterus contracts with each contraction giving a bolus of fluid into the maternal circulation each time

Question 23

at what stage of labour does CO increase the most?

Answer 23

third stage - 80%
2nd stage - 45%
1st stage - 30%
latent stage - 15%

Question 24

what are respiratory adaptations in pregnancy?

Answer 24

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

Question 25

what mechanical changes occur in response in pregnancy?

Answer 25

uterus expands, 
lower ribs flare 
diameter of chest increases 
thus diaphragm raised by 5cm 
chest wall compliance decreases

Question 26

why is responsible adaptations important for anaesthetists?

Answer 26

can be difficult to intubate/ventilate due to oedema, breasts, fetus
pre-oxygenation for 3 minutes! buys time

Question 27

what are the haematological adaptations of pregnancy?

Answer 27

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

Question 28

what is an important haematological factor to identify that can cause maternal death?

Answer 28

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

Question 29

what are the structural renal adaptations in pregnancy?

Answer 29

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)

Question 30

what are the functional renal adaptations of pregnancy?

Answer 30

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

Question 31

what are the GI adaptations in pregnancy?

Answer 31

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)