Chapter 14 - Amniotic Fluid

Amniocentesis

________ is recommended when blood screening tests and ultrasonography yield results that are abnormal.

Initial exposure

________ to foreign red cell antigens occurs during gestation and delivery of the placenta, when fetal red blood cells enter into the maternal circulation and stimulate the mother to produce antibodies to the antigen.

Specimens

________ are centrifuged at 2000 g for 10 minutes and examined at a wavelength of 650 nm.

Sphingomyelin

________ is also produced at a constant rate after about 26 weeks gestation and can serve as a control on which to base the rise in lecithin.

LBCs

________ performed on amniotic fluid stored at 4°C are stable for up to 10 days.

HDN

Fluid for bilirubin analysis in cases of hemolytic disease of the newborn (________) are placed in amber- colored tubes or covered with a black plastic cover to protect from light.

optical density

The ________ (OD) of the fluid is measured in intervals between 365 nm and 550 nm and the readings plotted on semilogarithmic graph paper.

Biochemical substances

________ produced by the fetus can be analyzed by fluorescence polarization and thin- layer chromatography to evaluate the health of the fetus.

L S

As the fetal lung matures, increased lamellar body production is proportional to the increase in amniotic fluid phospholipids and the ________ ratio.

fetal lung maturity

Fluid for ________ (FLM) tests should be placed in ice and can be refrigerated or frozen up to 72 hours prior to testing.

normal saline

A control may be prepared by diluting commercial chemistry control sera 1 to 10 with ________ and treating it in the same manner as the patient specimen.

outside edge

If a continuous line of bubbles forms around the ________, it indicates a sufficient amount of phospholipid is available to reduce the surface tension of the fluid even in the presence of alcohol, an antifoaming agent.

Filtration

________ is recommended for FLM methods to prevent loss of the phospholipids.

accurate gestational age

A(n) ________ is an important consideration in interpreting the results.

enzymes

The fluid also contains biochemical substances that are produced by the fetus, such as bilirubin, lipids, ________, electrolytes, nitrogenous compounds and proteins.

preterm delivery

A(n) ________ is usually considered to be a relatively safe procedure.

Respiratory distress

________ occurs in the presence of an L /S ratio of 2.0.

Failure

________ to swallow results in accumulation (polyhydramnios) and is an indication of fetal distress.

FLM

The surfactants responsible for ________ are produced and secreted by the type II pneumocytes of the fetal lung and stored in the form of structures termed lamellar bodies at about 20 weeks of gestation.

Albumin

________ is used as an internal standard in the same manner as sphingomyelin because it remains at a constant level throughout gestation.

fetal distress

Fluid for chromosome analysis is usually collected at approximately 16 weeks gestation, whereas tests for ________ and maturity are performed later in the third trimester.

Lecithin

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

hollow needle

A thin, ________ is inserted through the mothers abdomen into the mothers uterus and into the amniotic sac to aspirate the amniotic fluid.

neural tube disorders

It is often associated with ________, fetal structural anomalies, cardiac arrhythmias, congenital infections or chromosomal abnormalities.

Oligohydramnios

________ may be associated with umbilical cord compression, resulting in decelerated heart rate and fetal death.

Hemolytic disease of the newborn

________ caused by Rh blood type incompatibility.

Amniotic fluid

________ is present in the amnion, a membranous sac that surrounds the fetus.

Respiratory distress syndrome

________ (RDS) is the most frequent complication of early delivery and is a cause of morbidity and mortality in the premature infant.

Lamellar body diameter

________ is similar to that of small platelets; therefore, lamellar body counts (LBCs) can be obtained rapidly with use of the platelet channel of hematology analyzers.

immunologic agglutination test

The ________ for phosphatidyl glycerol is more rapid and does not require a laboratory to be equipped to perform thin- layer chromatography.

Sample results

________ are calculated from the stored standard curve using polarization values generated for each sample.

cellular elements

All fluid for chemical testing should be separated from ________ and debris using centrifugation or filtration as soon as possible to prevent distortion of chemical constituents by cellular metabolism or disintegration.

AFP

________ is the major protein produced by the fetal liver during early gestation (prior to 18 weeks)

maximum absorbance

The ________ of oxyhemoglobin occurs at 410 nm and can interfere with the bilirubin absorption peak, but it can be removed by extraction with chloroform if necessary.

trimester

After the first ________, fetal urine is the major contributor to the amniotic fluid volume and it is regulated by fetal swallowing.

mechanical screening test

It is a(n) ________ used to determine the presence of individual lung- surface lipid concentrations.

normal fluid

In ________, the OD is highest at 365 nm and decreases linearly to 550 nm, illustrated by a straight line.

Dye

________ bound to surfactant has a longer fluorescence lifetime and exhibits low polarization, whereas ________ bound to albumin has a decreased fluorescence lifetime and has high polarization.

fetal swallowing

Increased ________, urinary tract deformities and membrane leakage are possible causes of decreased amniotic fluid (oligohydramnios)

bilirubin absorption

When bilirubin is present, a rise in OD is seen at 450 nm because this is the wavelength of maximum ________.

Amniocentesis

________ may be indicated at 15 to 18 weeks of gestation for the following conditions to determine early treatment or intervention:

Specimens

________ for cytogenetic studies are maintained at room temperature or body temperature (37°C incubation) prior to analysis to prolong the life of the cells needed for analysis.

Amniotic fluid

________ has a composition similar to that of the maternal plasma and contains a small amount of sloughed fetal cells from the skin, the digestive system and the urinary tract.

amniocentesis

In general, ________ is a safe procedure, particularly when performed after the 14th week of gestation.

Amniotic fluid

________ is obtained by needle aspiration into the amniotic sac, a procedure called amniocentesis.

respiratory distress syndrome

This disease is caused by a lack of lung surfactant.

neural tube defects

What does increased AFP indicate?

induction of labor or intrauterine exchange transfusion

What is needed when the values on the Liley graph are at zone III?

meconium

What does dark green amniotic fluid indicate?

fetal death

what does dark red-brown amniotic fluid indicate?

refrigerated or frozen

How are specimens for FLM tests stored?

after the 14th week of gestation

When is amniocentesis the safest to perform?

maternal urine

A dried vaginal fluid specimen observed under a microscope has no crystals. Is it amniotic fluid or maternal urine?

increase, decrease and decrease, respectively

When fetal urine production starts, what happens to the concentration of nitrogenous products, glucose and proteins?

fetal urine and fetal swallowing

What controls the volume of amniotic fluid after the first trimester?