1What membrane contains amniotic fluid?
amnion
2What is the purpose of amniotic fluid?
to protect fetus
3What structures produce amniotic (initially)?
amnion and the placenta
4How does the fetus play an active role in the amniotic fluid?
by swallowing, respiration, and urination
5What is the volume of amniotic fluid through pregnancy?
25-50 mL at 12 weeks
800-1200 mL at 37 weeks
6What are the reasons for amniocentesis testing?
1. Diagnosis of genetic / congenital disorders early (15-18 wks)
2. Assessment of fetal lung maturity (32-42 wks)
3. Estimate and monitor degree of fetal distress
7How do you collect fluid for amniocentesis?
aseptic technique, sterile needle. collect 10-20 mL and place to sterile containers. Protect from light and transport immediately
8What is unique for amniotic fluid compared to urine?
amniotic fluid has ...
glucose
protein (2-8 g/L)
creatinine similar to plasma
9What is unique for (healthy) urine when compared to amniotic fluid?
urine has ...
NO glucose, NO protein, HIGH creatinine, and HIGH urea
10What is the problem for pts with diabetes or kidney disease?
may have presence of glucose and protein in urine
11What is the best indicator for determining if fluid is urine or amniotic fluid?
high urea content (urine)
12What is normal urine color?
colorless or pale yellow
13What causes the darker yellow to amber color in urine?
bilirubin
14What causes green urine?
meconium from fetal intestine
15What causes pale pink to red urine?
blood or hemoglobin
16Although all amniotic fluid is turbid, what changes in late pregnancy?
Early pregnancy not much particulate, late pregnancy is more turbid and has increased fetal cells, hair, and vernix in fluid
17What is the last organ to mature in fetuses?
pulmonary system
18When do you test for fetal lung maturity?
at 32+ weeks
19What is the purpose of the chemicla exam of fetal lung maturity?
to assess fetus viability outside of uterus
20What is the most common cause of death in newborns?
respiratory distress syndrome (RDS)
21What happens in respiratory disease syndrome (RDS)?
insufficient production of surfactant in newborn's lungs
22What is surfactant?
Compound that lowers the surface tension between 2 things;
mixture of fats & proteins made in lungs. surfactant coats the alveoli and prevents from sticking together when baby breathes.
23What correlations indicate possible RDS?
correlation between fetal lung maturity and level of specific phospholipids in amniotic fluid
24What 2 factors determine the probability of RDS?
1. results of fetal lung maturity (RLM) tests
2. gestational age of fetus at time of testing
25What is the recommended approach for testing for RDS?
cascade approach: series of FLM tests performed until a mature result is obtained or all tests are done
26What is the purpose of phospholipids fetal lungs?
to decrease surface tension (surfactants)
27What is lecithin?
major pulmonary surfactant
28What is sphingomyelin?
phospholipid in cell membranes
29What is the level of lecithin and sphingomyelin at 33 weeks?
both are the same
30What happens to the ratio of lecithin and sphingomyelin at 34-36 weeks?
lecithin increases
sphingomyelin stays constant or decreases
31What does L/S ratio of >2.5 mean?
maturity of fetal lungs
32What is the L/S ratio when the fetal lungs are matured?
>2.5
33How is the L/S ratio determined?
by using thin-layer chromatography technique
34What happens when there is a presence of blood in a specimen when trying to determine L/S?
decreases a mature result and increases an immature result
35Should meconium-contaminated specimens be used?
no because they're unreliable
36L/S test is a better predictor of ___ than ____
maturity / immaturity
37When is phosphatidyl glycerol (PG) detectable?
at 35 weeks gestation
38What are the methods to find phosphatidyl glycerol?
1. thin-layer chromatography
2. slide agglutination using anti-PG antibodies
39What test isnt affected by blood or meconium?
Phosphatidyl glycerol (PG) test
40What is the cons of PG test?
Positive tests are very specific (good) BUT many false negatives
41What does it mean when the L/S ratio is < 2.0 and is absent for phosphatidyl glycerol?
immature lungs
42What does it mean when the L/S ratio is ≥ 2.5 and absent for phosphatidyl glycerol?
indeterminate
43What does it mean when L/S ratio is < 2.0 but has trace for phosphatidyl glycerol?
indeterminate
44What does it mean when L/S ratio is ≥ 2.5 but has trace for phosphatidyl glycerol?
mature
45Where are pulmonary surfactants stored?
lamellar bodies
46How many lamellar bodies are present in the 3rd trimester?
50,000-200,000 lamellar bodies per microliter of amniotic fluid
47How does the TDx-FLM II test work?
it uses fluorescence polarization to evaluate amount of surfactant in relation to amount of albumin
48Why does the TDx-FLM II test for albumin?
because it is constant during the third trimester
49What is the ratio for surfactant / albumin for immature lungs?
< 40 mg / g indicate immature lungs
50What is the ratio for surfactant / albumin for mature lungs?
> 55 mg/ g indicate mature lungs
51What does bilirubin in amniotic fluid (yellow amniotic fluid) mean?
fetal erythroblastosis (hemolytic disease of the fetus)
52Allthough usually undetectable, what does bilirubin in amniotic fluid mean?
increased bilirubin means that there is significant fetal red blood cell hemolysis occuring
53What does the amount of bilirubin correlate with?
severity of hemolysis
54What is the absorbance line for normal amniotic fluid?
straight line from 365-550 nm
55What is the absorbance line for amniotic fluid with presence of bilirubin?
asorbance peak at 450 nm
56Why arent bloody specimens used when finding amniotic fluid bilirubin?
because oxyhemoglobin absorbs at 412-540 nm
57Why should amniotic fluid be specimens be protected from light?
bilirubin is very light sensitive