4. Maternal and Fetal Physiology Flashcards
blood travels from the mothers uterine artery to?
the placenta
from the placenta where does the blood go?
through the umbilical vein into the fetal right atrium
how is blood shunted around the liver in a fetus?
ductus venosus
what are the two pathways that blood can travel after being in the fetal right atrium?
50% blood shunt through foramen ovale to left atrium
50% blood goes through right ventricle
when blood makes it to the right ventricle what two ways can it go?
90% to pulm artery and is shunted to aorta via the ductus arteriosus
10% to the fetal lungs for perfusion
why does most of the blood shunt away from the fetal lungs (other than they aren’t breathing)
they have hypoxic vasoconstriction and that decreases the amount of blood that is able to flow through the lungs
how does blood return to the placenta?
umbillical artery
foramen ovale
hole between RA and LA
what % of the population have a patent foramen ovale?
10-25%
how quickly does functional closure of the foramen ovale take after birth?
rapidly after first breath
how quickly does anatomic closing of the foramen ovale take after birth?
3-12months
ductus arteriosus
connection between the pulmonary artery and the aorta
how quickly does functional closure of the ductus arteriosus take after birth?
first few days after birth
how quickly does complete closure of the ductus arteriosus take after birth?
4-6wk
what % of the population has a patent ductus arteriosus?
10%
what drug keep the ductus arteriosus open?
prostaglandins PGE1
indomethacin
promotes ductus arteriosus closure
treats PDA after birth
NSAIDS and ductus arteriosus
promotes closure of ductus arteriosus
contraindicated in third trimester pregnancy
what are the fetal circulation changes at birth?
- baby breathes = lung expands
- PaO2 incr = vasodilation of pulm vasculature
- incr pulm blood flow
incr blood flow to LA
LAP incr - incr LAP –> foramen ovale close
- incr Aortic P –> dectus arteriosus close
what triggers foramen ovale closur
incr LAP
what triggers ductus arteriosus closure?
incr aortic pressure
Maternal/Fetal blood flow order
uterus
uterine artery
placenta
umbilical vein
RA
ductus arteriosus or foramen ovale
aorta/systemic organs
umbilical arteries
placenta
umbilical vein
how much plasma ultrafiltrate do fetal lungs have?
90mL
how does the ultrafiltrate get removed from fetal lungs?
during SVD it is squeezed out by mothers pelvic muscles
the rest absorbed by pulm capillaries and lymphatics
which are more likely to have problems with respiration after birth? SVD or C-section
C-section, no squeeze of ultrafiltrate out
P50
PaO2 that will cause SaO2 of 50%
P50 normal adult hemoglobin
27mmHg
P50 pregnant mother at term
30mmHg
P50 fetal hemoglobin
19mmHg
which is more affinitive for oxygen? fetal or maternal hemoglobin?
fetal
Aortocaval compression
pregnant patient lays supine it compresses aorta and IVC
decrease CO
decrease uterine artery blood flow (fetal hypoxia)