AUBF 22: AMNIOTIC FLUID

is a product of fetal metabolism , with its components providing information on the fetus ' condition and development

Amniotic fluid

Amniotic fluid laboratory tests are essential in

monitoring fetal maturity and survival rate of the fetus in case of fetal distress

Amniotic fluid is found in

amnion

a sac or membrane composed of a single layer of cuboidal epithelial cells

amnion

Amniotic fluid is formed from

metabolism of fetal cells and fetal urine

functions of the amniotic fluid

1. exchange of water and chemicals between the fetus and maternal circulation

2. permit proper fetal lung development

3. stabilization of temperature to protect the fetus from extreme temperature changes

4. allows fetal movement

5. serves as a protective cushion for the fetus

The volume of amniotic fluid is regulated by its

( a ) production from fetal urine and lung fluid ( b ) absorption from fetal swallowing ( c ) intramembranous flow

refers to the absorption of amniotic fluid water and solutes into the fetal blood

Intramembranous flow

Volume of amniotic fluid at 12 weeks of gestation

25-50ml

Volume of amniotic fluid at 37 weeks of gestation

800-1200ml

amniotic fluid formation starts at the , where approximately of amniotic fluid is produced by the ___________ that is derived from the_________

1st trimester of pregnancy ; 35ml ; amnion and placenta ; maternal circulation or maternal plasma

In the later stages of pregnancy , ________________ play a significant role in the amniotic fluid volume and composition

fetal swallowing and urination

removes water and electrolyte from the amniotic fluid and replaces them through urination with metabolic by - products such as urea , creatinine , and uric acid

Fetal swallowing

removes metabolic waste products and replenishes them with water , nutrients , and electrolytes

maternal plasma

is the term if the amniotic fluid volume exceeds 1200mL

Polyhydramnios

is the term if the amniotic fluid volume is below 800mL

Oligohydramnios

is associated with decreased fetal swallowing and often indicates fetal distress and congenital fetal malformations in neural tube defect ( NTD ) , rapidly growing fetal edema , and hydrops fetalis

Polyhydramnios

It is secondarily associated with fetal structural anomalies , cardiac arrhythmias ( fetal heart failure ) , congenital infections and chromosomal abnormalities

Polyhydramnios

associated with increased fetal swallowing with a possible indication of urinary tract deformities , membrane leakage , donor twin transfusion syndrome , congenital malformation , premature rupture of the amniotic membrane and umbilical cord compression resulting in decelerated heart rate and fetal death

oligohydramnios

The ultimate source of amniotic fluid water and solutes is the

placenta

biochemical substances in amniotic fluid that can be used for the assessment of the fetus ' condition and development

bilirubin , lipids , enzymes , electrolytes , urea , creatinine, uric acid , proteins , and hormones

Their presence in amniotic fluid is also significant since these components serve as biochemical markers to detect neural tube defects

alpha fetoprotein and acetylcholinesterase

Once fetal production begins , what are the state of each component of amniotic fluid (increase or decrease)

increase in concentration in creatinine , urea , and uric acid decrease in glucose and protein Unffected is electrolytes, enzymes, hormones and metabolic end products

The collection of amniotic fluid is performed through

amniocentesis

Procedure in amniocentesis

1. Needle is introduced into the amniotic sac

2. 10-20mL or maximum of 30mL is aspirated in a sterile syringe , discarding the first 2-3 ml

Wh do we discard the first 1-2ml during amniocentessis

since it might be contaminated with maternal blood , tissue fluid and cells

Amniocentesis can either be

transabdominal or vaginal

Upon collection , amniotic fluid is placed in an

amber - colored container or aluminum foil .

T OR F: Glass containers should be avoided for containing amniotic fluid because cells will adhere to it , affecting the test result .

TRUE

When is amniocentessis typically performed

after 14 weeks ' gestation

At what week of gestation do we perform amniocentessis when Mother's age is 35 or more at delivery

15-18 weeks

At what wweek do we perform amnicentesis when there is a Family history of chromosomal abnormalities ( e.g. , Down syndrome )

15-18 weeks

At what week do we perfor amniocentessi when the Parent is known to have chromosomal abnormality - previous child with chromosomal abnormality

15-18 weeks

At what week d we perfoem amnicentesis when Parent is a carrier of a metabolic disorder

15-18 weeks

At what wek do we perform amniocentesis when there is History of genetic diseases such as sickle cell disease , Tay - Sachs disease , Hemophilia , muscular dystrophy , sickle cell anemia , Huntington's disease , and cystic fibrosis

15-18 weeks

At what week of gestation do we peforma amniocentesis for assessment of genetic defect / chromosome analysis

16th week of gestation

At what week of gestation do we perform amniocentesis for assessment of uterine growth restriction

Near end of 2nd trimester

At what week of gestation do we perform amnicentesis when there is Elevated maternal alpha fetoprotein

15-18 weeks

At what week of gestation do we perform amniocentessis when tgere is History of three or more miscarriages

5-18 weeks

This weekof gesttaion for amniocentesis is used to assess the pulmonary and overall health status of the fetus

20-42 weeks

This week of gestation is used to evaluate fetal lung maturity

20-42 weeks

This wek of gestation is used to assess fetal distress ( such as in cases of hemolytic disease of the newborn caused by Rh blood type incompatibility )

20-42 weeks

This weekk of gestation for amniocentesis is used to evaluate possible toxemia , diabetes mellitus and infection

20-42 weeks

First trimester is what week of pregnancy

Week 1 to Week 12 of pregnancy

Second trimester is what week of pregnanyc

Week 13 to Week 27 of pregnancy

Last trimester is what week of preganncy

Week 28 to Week 40 of pregnancy

For Fetal Lung Maturity Test ( FLM ) , the specimen must be placed on ________ for delivery to the laboratory and refrigerated before testing within _________

ice; 72 hours

For Fetal Lung Maturity Test ( FLM ), the specimen may be transported at room tempertuer as long as it wll be tested for _____________

16-24 hours

when determining the lecithin / sphingomyelin ratio ( L / S ratio ) , _________ centrifugation speed is applied for no longer than _________ @ _________ with the recommended filtration method to prevent ______________

low; 5 minutes; 500-1000 x g; loss of phospholipids

Specimen for these tests ( cell culture and chromosomal studies ) should be maintained at

and chromosomal room temperature or body temperature

For cell culture , it would require _________ centrifugation of the sample

140 x g

T OR F: For chemical assay, There is a need to separate cellular elements from debris as soon as possible to prevent distortion of chemical constituents by cellular metabolism and disintegration

TRUE

For chemical assay, Determination of phospholipid would require a centrifugation of _________ for __________

500 to 1000 x g; 5 minutes

The normal color of amniotic fluid is

colorless to pale yellow

amniotic fluid Color usually an indication of traumatic tap , abdominal trauma , or intra - amniotic hemorrhage

Blood - streaked

Blood - streaked color variation IS CORRELATED WITH

KLEIHAUER - BETKE test

This test determines the source of blood , either maternal or fetal

KLEIHAUER - BETKE test

If blood is present in the sample , the specimen should be________ immediately to _______________ before hemolysis occurs . Hemolysis causes the formation of __________ which can interfere with several chemical analyses

centrifuged; remove any intact red blood cells; oxyhemoglobin

These cells appear uncolored ghosts or dull red and contains poorly stained intermediate cells under kleihauers betke test

maternal cells

These cells would demonstrate resistance and appear as large , red and refractile cells nder kleihauers betke test

fetal cells

A yellow or amber colored amniotic fluid is often related to __________ in cases of ____________

bilirubin; hemolytic disease of the newborn ( HDN ) .

A dark green colored amniotic fluid indicates the presence of

meconium

a gelatinous or mucus - like material that forms in the fetal intestine due to swallowed amniotic fluid and fetal intestinal secretions

meconium

T OR F: fetal distress do not cause premature release of meconium into the amniotic fluid

FALSE. fetal distress can cause premature release of meconium into the amniotic fluid .

A dark red - brown amniotic fluid often indicates

fetal death

Amniotic fluid would usually have a

slight to moderate turbidity

turbidity of amniotic fluids accounts for the presence of

fetal cells , hair , and vernix

To remove particulate matter causing the turbidity , perform ___________

centrifugation and filtration

What ar ethe chemical test for fetal age

Amniotic fluid creatinine determination

Whata re the chemical test for fetal distress

1. Pigment analysis-color variation assessment

2. Alpha-fetoprotein test

3. Acetylholinesterase

4. Bacterial count

Chemical etst for fetal lung maturity

1. Lecithin-Spigoyelin ratio

2. Phosphatidyl glycerol determination

3. Foam stability index test/shake's/foam's testmicroviscotiy:flouorescene polaritzation assay

4. Lamellar body counting

This test is done by utilizing serum method- Jaffe's reaction

Amniotic fluid creatinine determination

Normal level of creatinine before 36th week of gesttaion

1.5 and 2.0 mg / dL

Creatinin elevel above 2.0 mg/dl indicates

fetal age greater than 36 weeks

In normal pregnancy , bilirubin in amniotic fluid is low and undetectable at

10-30 mg / dl

Increase in bilirubin is caused by

maternal antibodies cross the placenta and destroy the fetal cells

The measurement of amniotic fluid bilirubin is performed by

spectrophotometric analysis

In spectrophotometry analysis for blirubin, The optical density ( OD ) of the fluid is measured in intervals between

365 nm and 550 nm

When bilirubin is present , a rise in OD is seen at _______ because this is the wavelength of maximum bilirubin absorption

450 nm

What specmen prep is need for the determination of bilirubin levels

immediately centrifuged to remove spectral interference from cells , meconium and oxyhemoglobin

major protein produced by the fetal liver during early gestation ( before 18th weeks ) wherein maximal production is observed at 12th 15th week then eventually declines

Alpha - fetoprotein

found in the maternal serum due to combining fetal - maternal circulation and in the amniotic fluid from diffusion and excretion of fetal urine

Alpha - fetoprotein

indicated when maternal serum levels are elevated , a family history of previous neural tube defects exists or if there is history of multiple pregnancies

Measurement of amniotic fluid AFP levels

In most cases , increased levels of AFP in both the maternal circulation and the amniotic fluid can be indicative of

fetal neutral tube defects such as in anencephaly and spina bifida

Normal range of AFP

less than 2 MoM

If teh AFP is greater that 2MoM, it is indicative of

abnormal for maternal serum and amniotic fluid

Elevated concentration of acethycholinesterase is an indication of

neural tube defect

It is also a confirmatory test after an elevated amniotic fluid AFP level

Acetylcholinesterase level

Can acetylcholinesterase level be performed on bloody secimen?

NO. ACETYLCHOLINESTERASE ( AChE ) is not performed on bloody specimens because blood contains ACHE

To be considered as an infection , concentration of bacteria present should

50 / ul of amniotic fluid

These tests are performed to detect respiratory distress syndrome ( RDS ) ,

Tests for Fetal Lung Maturity ( FLM )

the most frequent complication of early delivery and is a cause of mortality in the premature infant

respiratory distress syndrome ( RDS ) ,

would usually result from insufficient production of lung surfactant and structural immaturity of fetal lungs

respiratory distress syndrome ( RDS ) ,

alveolar epithelial cells

type II pneumocytes

produce and secrete about 90 % of phospholipids and 10 % proteins in the form of lamellar bodies

type II pneumocytes

when viewed in electron microscopy , have a characteristic of layered or onion - like appearance

Lamellar bodies

They release surface - active compounds known as surfactants

Lamellar bodies

reduce the alveoli ' surface tension to prevent them from collapsing during expiration and reduce the amount of pressure needed to reopen the alveoli during inspiration

Surfactants

T or f: RDS increases with increasing gestational age and lung maturity

FALSE. RDS DECREASES with increasing gestational age and lung maturity

the primary component of surfactants ( phospholipids , neutral lipids , and protein ) that reduces alveoli tension to prevent it from collapsing

Lecithin