Amniotic Fluid Flashcards
sac that surrounds amniotic fluid
amnion sac??
2 layers of amnion sac
amniotic membrane and chorion membrane
function of amniotic sac
-cushion to help prevent injury to fetus
-matrix for moving nutrients and waste products in and out
-sac grows with baby – serves as cushion
-maintain even temp
where does fluid come from
derived through different sources of pregnancy
where does fluid come from Beginning of preg
comes from placenta and amnion
-Made of same matrix as maternal serum
where does fluid come from as pregnancy continues?
Fluid from lung fluid (develops as baby develops)
where does fluid come form last part of pregnancy?
Baby’s urine contributes to amount of fluid
during 3rd tri fluid is maintained by
through fetal urination and fetal swallowing amniotic fluid – SWALLOWING is important part in determining baby is healthy
fluid volume
increases throughout pregnancy
how much fluid in 1st tri
60 mL
how much fluid last tri until birth
800 mL-1200 mL
> 1200 mL
polyhydramnios : wrong with fetal swallowing (can be determined by ultrasound)– seen in neural tube defects
<800 mL
oligohydramnios : indicates congenital malformation/ premature rupture of amniotic membrane
composition of amniotic fluid
similar to maternal fluid
-electrolytes, glucose, etc
-cells unique to fetus
specimen collection
amniocentesis- only trained physician should preform
what is recommended for aminocentesis?
do not do prior to 14 weeks gestation (not enough fluid to be safe)
how is amniocentesis guided?
ultrasound
what is max amount to withdraw for amniocentesis?
30 mL
2 different ways to do amniocentesis?
intraabdominal and transvaginal
intraabdominal
most common way to do -can sterilize
transvaginal
easier method, but higher risk because risk of bacteria
reasons to perform amniocentesis
-mother is older/ history of miscarriage or birth defects
-find out lung maturity
what age should get an amniocentesis
> 35
1 concern of premature babies
lung immaturity
amniotic fluid is a what procedure
stat
-should be brought to lab ASAP
if fetal lung immaturity needs to be done how should sample be kept
on wet ice as soon as collected and refrigerated if can’t be done immediately
why does fetal lung maturity be placed on wet ice immediately
lecithin decrease quickly after drawn
if possible HDN what are you looking for
increase levels in bilirubin
(keep specimen away from light)
for cytogenetic studies how should specimen be kept
RT or 37 degrees and treated aseptically
what test does not get centrifuged
fetal lung maturity
normal appearance of amniotic fluid
clear or slightly yellow
when would amniotic fluid be slightly turbid
3rd tri
what does blood tinged amniotic fluid mean
intra abdominal hemorrhage or HDN
what does dark red amniotic fluid mean?
baby is in bad danger or has died already
if RBCs are present in amniotic fluid need to determine if mother origin or fetal; how is this done
Kleihauer Betke Stain
Kleihauer Betke Stain principle
fetal Hgb is resistant to acid elution and adult Hgb is not
fetal cells= darker
mother= ghost cells
(we now do flow cytometry)
what does green amniotic fluid mean?
presence of meconium - baby poop
large amounts dangerous to baby– they can choke on it
1st reason for amniocentesis??
HDN
1 cause of HDN
Rh incompatibility and sometimes ABO
what kind of bili in HDN
unconjugated
how is amount of bili measured
spectrophotometer
-most can’t be measured due to turbidity of sample
amount of bili directly proportional to
severity of hemolysis
-serial measurements taken at different intervals
what is measured on semi log paper
absorbance versus wavelength
normal fluid= straight line decrease
what does semi log paper show when bili present
450 nm peak
liley graph bilirubin plots
absorbance versus gestational age
best done as 20-40 weeks
liley graph: zone 1
midly affected fetus
zone 2
moderately affected fetus– decide if intervention is needed (depends on weeks preg)
zone 3
severely affected fetus, intervention is needed
quean chart??
starts at 14 weeks
draw backs in amniotic fluid
-keep out of light
-no meconium- will interfere
-if has blood– peaks at 410 nm and misinterpreted as bili peak
if doing amniotic fluid should not be done before
13 weeks
most common neural defect
spina bifida
other kind of neural defect
anisufily??
-not compatible with life: born with no brain
if neural defect suspected what us first drawn
alpha fetoprotein on mother’s serum
produced by fetal liver and crossed to maternal serum
alpha fetal protein depends on
gestational age of fetus, mother’s weight, diabetic, smoker
changes each week
if doesn’t match gestational age
will do by amniotic fluid
increases in alpha fetoprotein
neural tube defect
decrease in alpha feto protein
down syndrome
how to prevent neural tube defect
folic acid, vitamin B12
what is also drawn with alpha feto protein levels
acetyl colin esterase
-should not be present in normal pregnancy
-can’t be run if bloody
-present in neural tube defects
1 complication of early term delivery
fetal lung maturity/ respiratory distress
fetal lung immaturity is due to
insufficient surfactant which helps the lungs mature
why is surfactant important
so lungs do not collapse in exposure to oxygen during delivery
tests for surfactant should not be done before
30 weeks
-they will negative because not a normal amount of surfactant
3 tests for maturity
- Lecithin levels
- Spengolmylein levels
- Phosphatidyl glycerol
first thing you look for fetal lung maturity
lecithin: splengomylein ratio
what is primary surfactant that indicates lung maturity
lecithin
what week is lecithin produced at a stable rate
35th
what is produced at a fairly constant ratio during gestation
spenglomylein
what is normal fetal lung maturity at 35th week
2:1
what is fetal lung maturity ratio for diabetic mothers
2.5 :1
term given to immature lungs
RDS- respiratory distress syndrome
(use to be reason for crib death)
beside L/S ratio what else is needed to be seen for lung maturity
Phosphatidyl glycerol
L/S ratios performed by
old: thin layer chromatography
now: immunoassays
need to be followed when testing for fetal lung maturity
- amnio fluid can’t have meconium or blood
- amniotic fluid needs to be placed on wet ice or refrigerated asap
- phosphatidyl glycerol done on immunoassays
what test does blood and meconium not interfere with testing and is done after 35 weeks
Phosphatidyl glycerol- immunoassays
screening test for fetal lung
shake test/ foam stability test
test for foam stability
○ Amniotic fluid mixed with 95% ethanol
○ SHAKE for 15-20 sec
○ Sit for 15 min untouched
○ If enough surfactant= layer of bubbles at the top that remain for 15 min
○ Blood and meconium will interfere with this test
TEST for fetal lung
lamellar bodies count
when surfactant is made it is stored in
lamellar bodies
-when become filled enter amniotic fluid
-more surfactant= more found
what can lamellar bodies not be contaminated with
blood- contains platelets
amniocentesis can be used to determine
gestational age
how does amniocentesis work with determining gestational age
look for measurement of creatinine values for muscle mass
> 3mg/dL indicate mature infant
what test determines preterm risk / trauma to baby delivery
fetal fibronectin
when are fetal fibronectin values high
beginning of preg because fibrin formed to hold baby in place
when do fetal fibronectin levels decrease
once formed- levels decrease until baby is ready to be born and breaks down
when should fetal fibronectin be done
22-35 weeks
what indicates women at higher risk for preterm delivery
> 50 ng/mL
