18. Physiology of Pregnancy Flashcards
(29 cards)
demands of the foetus
nutrients (O2, amino acids, glucose)
amniotic fluid production
removal of foetal waste products (CO2, nitrogen compounds)
plasma volume
increases by 40% 2.5 to 3.7 litre by end of pregnancy 11-13kg weight gain ~1 litre is contained within maternal blood spaces of the placenta \+prepares for blood loss during birth
plasma colloid osmotic pressure
falls
causes shift of fluid into extracellular space
increased hydration of connective tissue
oedema (lower limbs, hands, face)
how does plasma volume increase?
RAAS
oestrogen stimulates angiotensinogen secretion, eventually causing increased aldosterone secretion
+ progesterone stimulates aldosterone too
causes increased reabsorption of water and sodium
effect of ANP
slight decrease
decreases thirst threshold (increases fluid intake)
osmostat is rest - plasma volume increases
red blood cells in pregnancy
mass increases 25%
combats dilution anaemia caused by increased plasma volume
iron is required for increase in cell mass - more iron absorbed in gut and ferritin levels fall
should iron be supplemented in pregnancy?
no, unless twins
ferritin levels and iron absorption in the gut increases to provide all necessary iron
haemostasis
hypercoaguable state
increased: plasma fibrinogen, platelets, factor VII, von Willebrand factor
important during deliver: 500ml/min blood loss at placental separation
uterine artery
blood flow increases 3.5 fold in pregnancy
95 to 345 ml/min
white blood cells
concentration does not fall - total WBC increases
more neutrophils
around delivery = marked increase
heart changes
enlarges by ~12%
innocent systolic murmurs (common, 90%)
diastolic murmurs - less common (20%) and require investigation
uterus pushing up against diaphragm may cause maternal heart to shift up in chest cavity
diastolic murmurs
may be innocent
further investigation to to rule out cardiopathies
change in cardiac axis/position may result tinc changes on ECG and X ray
peripheral resistance
peripheral vasodilation occurs due to progesterone
peripheral resistance is decreased by 35%
blood pressure
decreased resistance is partly compensated for
cardiac output increases
small change is observed
respiratory system
increased pulmonary blood flow is matched:
increased tidal flow
decrease in maternal pCO2 and increased maternal pO2
increased availability of O2 to tissues
- aids diffusion at placenta
effects of CV and respiratory changes
high blood flow maximises O2 on maternal side of placenta
foetal haemoglobin has higher affinity for O2 than adult
increased CO may increase flow to skin: aids heat loss
renal system
kidney increases 1cm in size
GFR and effective renal plasma flow increase by over 50%
tubular reabsorption capacity = unchanged- glucose reabsorption impaired
plasma creatinine and urea decrease
dilatation of renal pelvis and ureters (progesterone)
GI system
gastro-oesophageal reflux - up to 70% - due to increased abdominal pressure
slowing of gut motility and constipation (progesterone)
glucose metabolism in 1st trimester
increased sensitivity to insulin
increase glycogen synthesis and fat deposition
second trimester
insulin resistance
cortisol, progesterone, HPL and oestrogen = insulin antagonists
glucose levels may rise
+ increase in fatty acids- energy sources for foetus
folate importance
dan synthesis, repair and regulation
important for rapid cell division - embryos
deficiency in pregnancy associated with neural tube defects
folate in pregnancy
daily requirement increased from 50mg to 400mg
significant tissue stores: dietary deficiency may take months to become apparent
no need for supplementation, but can precent neural tube defects
thyroid funciton
increased iodine absorption increased serum T3 and T4 increased TBG unbound T3 and T3 levels remain the same mostly remains unchanged
hormones released by the placenta
protein hCG - human chorionic gonadotrophin hPL - human placental lactogen hPG - human placenta gonadotrophin CRH - corticotrophin releasing hormone steroid progesterone oestrogen (oestradiol)
