AMNIOTIC FLUID Flashcards by mt corner

Membranous sac that surrounds the fetus

Amnion

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Primary functions of amniotic fluid:

Provide protective cushion for fetus
Allow fetal movement
Stabilize temperature to protect fetus from extreme temperature changes
Permit proper lung development

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The absorption of amniotic fluid water and solutes into the fetal vascular system is termed as ____________.

Intramembranous flow

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TRUE or FALSE:

Amniotic fluid volume is regulated by a balance between the production of fetal urine and lung fluid and the absorption from fetal swallowing an intramembranous flow.

TRUE

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Amount of amniotic fluid during the third trimester of pregnancy

800-1200 mL

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The amount of amniotic fluid (increases/decreases) in quantity throughout pregnancy and then (increases/decreases) prior to delivery.

Increases; decreases

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Amniotic fluid volume of >1200 mL is termed __________.

Polyhydramnios

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Amniotic fluid volume of <800 mL is termed __________.

Oligohydramnios

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TRUE or FALSE:

Cases of polyhydramnios and oligohydramnios may both result in some falsely low or falsely high analytes.

TRUE

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Average amniotic fluid volume

1000 mL

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During the first trimester, what is the approximate volume of amniotic fluid that come from the maternal circulation?

35 mL

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During each episode of fetal respiratory movement, secreted lung liquid enters the amniotic fluid, bathing the lungs and washing pulmonary and alveolar contents such as _________, __________, and ___________. These lung surfactants also serve as index of fetal lung maturity.

Lecithin
Sphingomyelin
Phosphatidyl glycerol

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This is the primary contributor to the amniotic fluid volume after the first trimester

Fetal urine

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TRUE or FALSE:

When fetal urine production occurs, fetal swallowing of amniotic fluid also begins.

TRUE

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Polyhydramnios or Oligohydramnios:

Failure of fetal swallowing

Polyhydramnios

Note: Failure of the fetus to begin swallowing results in excessive accumulation of amniotic fluid

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Polyhydramnios or Oligohydramnios:

Excessive fetal swallowing

Oligohydramnios

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Polyhydramnios or Oligohydramnios:

Associated with neural tube disorders

Polyhydramnios

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Polyhydramnios or Oligohydramnios:

May be caused by urinary tract deformities and membrane leakage

Oligohydramnios

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The ultimate source of amniotic fluid water and solutes

Placenta

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TRUE or FALSE:

Amniotic fluid has a composition similar to maternal plasma

TRUE

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Biochemical markers for neural tube defects

Alpha-fetoprotein
Acetylcholinesterase

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When fetal urine production begins, the amniotic fluid composition changes. Indicate whether the indicated analyte will INCREASE or DECREASE:

Creatinine

INCREASE

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When fetal urine production begins, the amniotic fluid composition changes. Indicate whether the indicated analyte will INCREASE or DECREASE:

Urea

INCREASE

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When fetal urine production begins, the amniotic fluid composition changes. Indicate whether the indicated analyte will INCREASE or DECREASE:

Uric acid

INCREASE

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When fetal urine production begins, the amniotic fluid composition changes. Indicate whether the indicated analyte will INCREASE or DECREASE: Glucose

DECREASE

When fetal urine production begins, the amniotic fluid composition changes. Indicate whether the indicated analyte will INCREASE or DECREASE: Protein

DECREASE

TRUE or FALSE: Upon production of fetal urine, concentrations of electrolytes, enzymes, hormones, and metabolic end-products in the amniotic fluid also vary and are highly significant.

FALSE Note: They are of little significance

Which particular analyte in the amniotic fluid may be used to determine fetal age?

Creatinine

Amniotic fluid creatinine level prior to 36 weeks’ gestation

1.5 – 2.0 mg/dL

Amniotic fluid creatinine level at >36 weeks’ gestation

>2.0 mg/dL

Analytes that may aid in the differentiation between amniotic fluid and maternal urine

Creatinine Urea Glucose Protein Note: Creatinine & Urea: More reliable Glucose & Protein: Less reliable

Levels of creatinine and urea are (higher/lower) in amniotic fluid than in urine.

Lower

Creatinine levels in amniotic fluid

<3.5 mg/dL

Urea levels in amniotic fluid

<30 mg/dL

Creatinine levels in maternal urine

As high as 10 mg/dL

Urea levels in maternal urine

As high as 300 mg/dL

Presence of glucose, protein, or both is associated more closely with (amniotic fluid/maternal urine).

Amniotic fluid

This is a test that can differentiate amniotic fluid from urine and other body fluids. It can also be used to evaluate premature rupture of the membranes. In this test, vaginal fluid specimen is spread on a glass slide, completely air-dried at RT, and observed microscopically.

Fern test

In performing fern test, the vaginal fluid specimen spread on a glass slide must be completely air-dried at what condition/temperature? A. Refrigerated B. Frozen C. Room temperature

C. Room temperature

The presence of fern-like crystals that is considered a positive screen for amniotic fluid is composed mainly of ____________.

Protein Sodium chloride

Process of collection of amniotic fluid

Amniocentesis

In general, amniocentesis is a safe procedure, particularly when performed after the ______ week of gestation.

14th

When testing for chromosome analysis, amniotic fluid is usually collected at approximately ________ week of gestation.

16th

At what part of pregnancy is amniocentesis performed when testing for intrauterine growth retardation?

Near the end of 2nd trimester

At what part of pregnancy is amniocentesis performed when testing for fetal distress and maturity?

3rd trimester

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Mother is ≥35 years old at delivery

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Family history of chromosome abnormalities

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Earlier pregnancy or child with birth defect

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Parent is a carrier of metabolic disorder

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Family history of genetic diseases

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Elevated maternal serum AFP

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Abnormal triple marker screening test

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Previous child with neural tube disorder

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Three or more miscarriages occurred

15-18 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: To detect fetal lung maturity

20-42 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Evaluate fetal distress

20-42 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Evaluation of HDN caused by Rh blood type incompatibility

20-42 weeks’ gestation

Determine whether amniocentesis is performed at 15-18 WEEKS’ GESTATION or 20-42 WEEKS’ GESTATION: Check for infection

20-42 weeks’ gestation

The type of amniocentesis that is most frequently performed is (vaginal/transabdominal).

Transabdominal

The type of amniocentesis that carries greater risk of infection is (vaginal/transabdominal).

Vaginal

How much amniotic fluid (in mL) is collected in sterile syringes when amniocentesis is performed?

30 mL

What volume of amniotic fluid may be contaminated by maternal blood, tissue fluid, and cells and must therefore be discarded?

First 2-3 mL

What must be the storage condition for amniotic fluid to be tested for fetal lung maturity?

Placed in ice for delivery to the laboratory and kept refrigerated

What must be the storage condition for amniotic fluid to be tested for cytogenetic studies or microbial studies?

Maintained at room temperature or body temperature prior to analysis

What must be the storage condition for amniotic fluid to be tested for bilirubin?

Immediately protected from light NOTE: This may be through the use of: * Amber-colored tubes * Wrapping the collection tube in foil * Use of black plastic cover for the container

What must be done to specimen for chemical testing prior to analysis?

Fluids must be separated from cellular elements and debris immediately to prevent distortion of chemical constituents by cellular metabolism or disintegration.

What process/es may be used to separate fluids from cellular elements and debris?

Filtration Centrifugation

Amniotic fluid color: Normal

Colorless

Amniotic fluid color: Traumatic tap

Blood-streaked

Amniotic fluid color: Abdominal trauma

Blood-streaked

Amniotic fluid color: Intra-amniotic hemorrhage

Blood-streaked

Amniotic fluid color: Hemolytic disease of the newborn

Yellow (due to bilirubin)

Amniotic fluid color: Meconium

Dark green

Amniotic fluid color: Fetal death

Dark red-brown

This is the term used to describe a newborn’s first bowel movement

Meconium

This is a test that can be used to determine the source of blood (maternal or fetal) present in the amniotic fluid

Kleihauer-Betke test (for fetal hemoglobin)

TRUE or FALSE: Amniotic fluid bilirubin is measured by spectrophotometric analysis using serial dilutions.

TRUE

The optical density of amniotic fluid is measured in intervals between _____ nm and ______ nm and the readings plotted on semilogarithmic graph paper.

Between 365 nm and 550 nm

In case of normal amniotic fluid, at what wavelength is the OD highest and at what wavelength does it decrease?

Highest at 365 nm, decrease linearly to 550 nm

When bilirubin is present in amniotic fluid, a rise in OD is seen at what wavelength?

450 nm NOTE: This is the wavelength of maximum bilirubin absorption

In spectrophotometric analysis of amniotic fluid bilirubin, the absorbance difference of OD at 450 nm is plotted on a ______________ to determine the severity of the hemolytic disease.

Liley graph

In spectrophotometric analysis of amniotic fluid bilirubin using Liley graph, which zone indicate non affected or mildly affected fetus?

Zone I

In spectrophotometric analysis of amniotic fluid bilirubin using Liley graph, which zone indicate moderate hemolysis and require careful monitoring anticipating an early delivery or exchange transfusion upon delivery

Zone II

In spectrophotometric analysis of amniotic fluid bilirubin using Liley graph, which zone indicate severe hemolysis/severely affected fetus?

Zone III

In spectrophotometric analysis of amniotic fluid bilirubin, what intervention must be considered when the absorbance difference of OD at 450 nm is plotted in Zone III?

Induction of labor Intrauterine exchange transfusion

Amniotic fluid for bilirubin testing must be protected from light since markedly decreased values will be obtained with as little as ____ minutes of light exposure.

30 minutes

Amniotic fluid contaminated with meconium will cause falsely (high/low) absorbance difference at 450 nm.

Low Note: Specimen contaminated with meconium are not acceptable for spectrophotometric analysis

Specimens for spectrophotometric analysis that are contaminated with blood are generally unacceptable. Maximum absorbance of oxyhemoglobin in the spectrophotometric analysis occurs at what wavelength?

410 nm

Interferences in OD 450 caused by blood may be removed with extraction through the use of what reagent?

Chloroform

Fetal neural tube defects such as anencephaly and spina bifida can be determined by (increased/decreased) levels of AFP in both the maternal circulation and amniotic fluid.

Increased

This is the major protein produced by the fetal liver prior to 18 weeks of gestation

Alpha-feto protein (AFP)

In the spectrophotometric analysis of amniotic fluid bilirubin, what variable is plotted in the x-axis?

Wavelength (nm)

In the spectrophotometric analysis of amniotic fluid bilirubin, what variable is plotted in the y-axis?

Absorbance

Serum and amniotic fluid AFP levels are reported in terms of MoM. What does MoM stand for?

Multiples of median

What is the normal/reference value of maternal serum and amniotic fluid AFP levels in terms of MoM?

<2 MoM

Upon determination of elevated amniotic fluid AFP levels, what analyte must be measured that is more specific than AFP for neural tube disorders and must not be performed on blood specimen?

Amniotic acetylcholinesterase (AChe)

The most frequent complication of early delivery and is the seventh most common cause of morbidity and mortality in the premature infant.

Respiratory distress syndrome (RDS)

RDS is caused by (excess/insufficiency) of lung surfactant production and structural immaturity of fetal lungs.

Insufficiency

The incidence of RDS (increases/decreases) with increasing gestational age and lung maturity).

Decreases

The reference method to which tests of fetal lung maturity are compared is the ________________.

Lecithin-sphingomyelin ratio

The primary component of surfactants (phospholipids, neutral lipids, proteins) that make up the alveolar lining and account for alveolar stability.

Lecithin

At what week of gestation is lecithin produced at an increased rate?

35th week of gestation NOTE: This is to stabilize the fetal lung alveoli

Sphingomyelin is a lipid produced at a constant rate after about ______ weeks’ gestation.

TRUE or FALSE: Both lecithin and sphingomyelin appear in the amniotic fluid in amounts proportional to their concentrations in the fetus.

TRUE

L/S ratio prior to 35 weeks’ gestation

<1.6 Note: This is because large amounts of lecithin are not produced during this time.

L/S ratio after 35 weeks’ gestation

≥2.0

TRUE or FALSE: Blood and meconium both contain lecithin and sphingomyelin.

TRUE NOTE: This is why they may cause falsely elevated L/S ratio.

Method used for quantitative measurement of lecithin and sphingomyelin.

Thin-layer chromatography (TLC)

TLC is used for quantitative measurement of lecithin and sphingomyelin. Due to heavy cost and labor, L/S ratio is replaced by what method/s?

* Quantitative phosphatidyl glycerol immunoassays * Lamellar body density procedures

At what week of gestation can phosphatidyl glycerol be detected?

After 35 weeks’ gestation

TRUE or FALSE: Production of lecithin and phosphatidyl glycerol are normally parallel to each other, except production of lecithin is delayed in cases of maternal diabetes.

FALSE Note: Phosphatidyl glycerol production is delayed in cases of maternal diabetes, not lecithin.

To provide an accurate measurement of fetal lung maturity, what must be included in the thin-layer chromatography lung profile?

* Lecithin * Sphingomyelin * Phosphatidyl glycerol

Amniostat-FLM principle

Agglutination of phosphatidyl glycerol

In Amniostat-FLM, a negative result is indicative of pulmonary (immaturity/maturity).

Immaturity

In Amniostat-FLM, a low positive or high positive is indicative of pulmonary (maturity/immaturity).

Maturity

This is a mechanical screening test to measure individual lung-surface lipid concentration wherein presence of bubbles indicates sufficient amount of phospholipid is available to reduce surface tension of fluid even in the presence of alcohol.

Foam test/Shake test

In Foam/shake test, amniotic fluid is mixed with ___% ethanol.

95%

In foam/shake test, how long is amniotic fluid mixed or shaken with 95% ethanol?

15 seconds

In foam/shake test, how long is amniotic fluid mixed with ethanol must be left undisturbed?

15 minutes

A modification of foam shake test where amniotic fluid is added to tubes containing increasing amounts of 95% ethanol.

Foam Stability Index

In foam stability index, what is the volume of amniotic fluid added to tubes containing increasing amounts of 95% ethanol?

0.5 mL

In foam stability index, 0.5 mL of amniotic fluid is added to tubes containing increasing amounts of 95% ethanol ranging from ____ mL to _____ mL in ______ increments.

0.42 mL to 0.55 mL; 0.01 mL

Foam stability index that indicates FLM.

≥47

Surfactant is composed of approximately ___% phospholipid and ___% protein.

90%; 10%

These are packed storage granules of pulmonary surfactant.

Lamellar bodies

What cells secrete lamellar bodies?

Type II pneumocytes of the fetal lung

Lamellar bodies are secreted at _____ weeks of gestation and are absorbed into the alveolar spaces to provide surfactant.

Lamellar bodies enter the amniotic fluid at about _____ weeks of gestation.

When lamellar bodies enter amniotic fluid, they increase in concentration from __________/uL to ___________/uL by the end of third trimester.

50,000/uL to 200,000/uL

The number of lamellar bodies is (directly/inversely) proportional to amount of phospholipid present in the fetal lungs.

Directly

Presence of lamellar bodies (increase/decrease) the OD of amniotic fluid.

Increase

For lamellar body count, specimens are centrifuged at _____ g for ______ minutes.

2000 g for 10 minutes

Lamellar bodies are examined using what wavelength?

650 nm

In testing lamellar bodies, what optical density (OD) is equivalent to L/S ratio of ≥2.0

OD 0.150

Lamellar body diameter is similar to the diameter of which cells?

Platelets

Lamellar body diameter is similar to that of small platelets ranging in size from __ to __ fL or ___ to ___ um.

1.7 to 7.3 fL; 1 to 5um

TRUE or FALSE: Lamellar body count may be performed using platelet channel of automated hematology analyzers using either optical or impedance methods for counting.

TRUE

Advantages of lamellar body counting

* Rapid TAT * Low reagent cost * Wide availability * Low degree of technical difficulty * Low volume of amniotic fluid required * Excellent clinical performance

Meconium and mucus may cause falsely (increased/decreased) lamellar body count.

Increased

Specimens for lamellar body counting must be stored at what temperature?

2C to 8C NOTE: Specimen must NEVER be frozen

For noncentrifuged samples, what lamellar body count indicates FLM?

≥50,000/uL

For noncentrifuged samples, what lamellar body count indicates immaturity of fetal lungs?

≤15,000/uL

Microviscosity testing (fluorescence polarization assay for FLM) is measured the ___________ratio and is based on the principle that phospholipids (increase/decrease) the microviscosity of amniotic fluid.

Surfactant to Albumin (S/A) ratio; decrease

TRUE or FALSE: Microviscosity testing is no longer performed.

TRUE

In microviscosity testing, what S/A ratio indicated FLM?

55 mg/g

In microviscosity testing, what S/A ratio (range) were considered to be indeterminate of FLM?

40 mg/g – 54mg/g

In microviscosity testing, what S/A ratio indicated immature fetal lungs?

≤39 mg/g