AMNIOTIC FLUID Flashcards
colorless to pale yellow color found in the membranous sac that surrounds the fetus known as Amnion
AMNIOTIC FLUID
AMNIOTIC FLUID Functions:
- cushion for fetus
- allows fetal movement
- stabilizes temperature
- proper lung development
Normal volume:
* the volume of the amniotic fluid ______throughout the pregnancy
* the volume of the amniotic fluid gradually ______ before delivery
Normal volume: 800-1200mL during the 3rd trimester
* the volume of the amniotic fluid increases throughout the pregnancy
* the volume of the amniotic fluid gradually decreases before delivery
ultimate source of amniotic fluid water and solutes
placenta
during the 1st trimester, ____ of amniotic fluid is derived from the circulation coming from the mother
35mL
the major constituent of amniotic fluid is fetal urine
After the 1st trimester
the fetus can already release lung fluid, which then contributes to the volume of the amniotic fluid
During the 3rd trimester
The normal volume of the amniotic fluid is regulated by the balance between the production of the fetal urine and lung fluid and absorption by:
- fetal swallowing of amniotic fluid and
- intramembranous flow
Increase in the normal volume of the amniotic fluid (more than 1200mL)
Polyhydramnios
Decrease in the normal volume of the amniotic fluid (less than 800mL)
Oligohydramnios
Happens when there is decrease in the fetal swallowing of the urine and neural tube defects
Polyhydramnios
- Happens when there is an increase fetal swallowing of urine
- Membrane leakage
- Urinary tract deformities (impaired
urination → decreased fetal urine production)
Oligohydramnios
Amniotic fluid Collection Method:
Amniocentesis
Maximum volume we collect:
30 mL
is discarded because it may be contaminated with maternal blood, tissue fluid, or cell
first 2-3mL
the amniotic fluid we collect can be subjected for chromosomal studies (e.g., to detect trisomy21/down syndrome)
2nd trimester (approx. 16th week of pregnancy)
can be used for assessment of fetal lung maturity and fetal hemolytic disease
3rd trimester
- The amniotic fluid should be placed on ice during delivery
- Must be kept refrigerated if you will not perform the test immediately
Test for fetal Lung maturity
Sample must be kept at room temperature or body temperature (37degC)
Test for Cytogenetic studies/Microbial studies
To assess HDN is to detect bilirubin in amniotic fluid
Test for HDN (Hemolytic Disease of the Newborn)
a photosensitive analyte and must be protected from light
Bilirubin
Use ________bottle as a specimen container
▪ Alternatives:
amber-colored; foil and black plastic cover
less reliable compared to urea and creatinine
Protein and glucose
cases that when a mother has proteinuria or glucosuria
false positive maternal urine
major metabolic products → high concentration in maternal urine
urea and creatinine
Urea Value in:
Amniotic Fluid
Maternal Urine
Urea Value in:
Amniotic Fluid <30mg.dL
Maternal Urine >30mg/dL
Creatinine Value in:
Amniotic Fluid
Maternal Urine
Creatinine Value in:
Amniotic Fluid <3.5mg/dL
Maternal Urine >10mg/dL
detects ruptured amniotic membranes, aside from the 4 analytes
Fern Test
Fern Test Specimen:
Vaginal fluid
presence of fern-like crystals due to protein and sodium chloride
Amniotic fluid
Amniotic fluid Appearance
Colorless to pale yellow
Normal
Traumatic tap, abdominal trauma, intraamniotic hemorrhage
Blood-streaked
Increased bilirubin (seen on HDN)
Yellow
Meconium (1st fetal bowel movement or newborn 1st poop)
Dark Green
Fetal death/Fetal demise
Dark red brown
Happens if there’s a presence of anti-D antibodies that can cross the placenta and destroys large number of fetal RBC → degradation of products (ie. Bilirubin)
HDN/ Erythroblastosis fetalis
test for HDN
Optical density 450 (OD450)
Absorbance of Amniotic fluid:
Increased at 365nm and decreased at 550nm
Normal
Absorbance of Amniotic fluid:
Increased at 450nm (wavelength of maximum bilirubin absorbance)
HDN
Results are plotted on a
Liley Graph
nonaffected/mildly affected fetus (normal fetus)
Zone I
moderately affected fetus and close monitoring is required to prevent severe effect of HDN
Zone II
severely affected fetus and requires interventions
Zone III
Interferences that may occur when performing this test:
o Presence of cells
o Presence of meconium
o Presence of debris
o Presence of Hgb – peak absorbance of Hgb is 410nm → high absorbance of amniotic fluid
