Amniotic Fluid Flashcards by Kyra Catedral

• The fluid that bathes the fetus throughout its gestation

Amniotic fluid

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• Fills the______, a membrane composed of a single layer of cuboidal epithelial cells

amnion

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• Protects the fetus while enabling_____

fetal movement

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FORMATION
• Changes throughout fetal gestation
• Early pregnancy: produced by the______ and ______

amnion and the
placenta from maternal plasma

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FORMATION

• Later stages of pregnancy
• Water-solute exchange between the fetus and the surrounding medium (product of fetal metabolism)
•_________
•_________

• Maternal plasma exchange

Fetal swallowing and fetal urination

Capillary exchange in the pulmonary system

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COLLECTION
• _________ is preferred
• With_____ examination

•________ may be done

• Transabdominal amniocentesis

ultrasonic

Vaginal amniocentesis

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• High risk of infection and possible contamination of vaginal cells

Vaginal amniocentesis

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COLLECTION

• Aspirate ______in several sterile syringes
• Discard the first____

10-20 ml

2-3 ml

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COLLECTION
• Typically collected after _____of gestation

14 weeks

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STORAGE

• For cell culture/chromosomal studies: preserve_____

in body or RT

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STORAGE

• For fetal lung maturity tests:

place in ice for delivery and refrigerated

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When to Perform Amniocentesis

Elevated maternal alpha-fetoprotein (suspect neural tube defect)

14-18 weeks

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When to Perform Amniocentesis
Previous child with neural tube defect

Parent is carrier of a metabolic disorder

14-18 weeks

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When to Perform Amniocentesis

Parent has known chromosomal
abnormality
Previous child with chromosomal
abnormality

14-18 weeks

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When to Perform Amniocentesis

Mother >35 years

14-18 weeks

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When to Perform Amniocentesis

Assessment of fetal lung maturity

20-42 weeks

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When to Perform Amniocentesis

• Infection

20-42 weeks

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When to Perform Amniocentesis

Assessment of fetal distress due to:
• Blood group incompatibility (e.g., Rh)

20-42 weeks

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VOLUME
• 12 weeks gestation:______
• 37 weeks gestation:______

25-50 ml

800-1200 ml

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• Decreased fetal swallowing, congenital fetal malformations

• Polyhydramnios

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• Polyhydramnios:

> 1200 ml

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•no amniotic fluid

• Anhydramnios

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• Premature rupture of amniotic membrane

Oligohydramnios

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Oligohydramnios

< 800 ml

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PHYSICAL EXAMINATION • Color • Normal:_______

colorless or pale yellow

: yellow or amber

• Presence of bilirubin

dark red-brown

• Fetal death

pale pink to red

• Blood contamination

green (gelatinous material that forms in fetal intestine as a result of swallowed AF and fetal intestinal secretions)

• Presence of meconium

PHYSICAL EXAMINATION • Transparency • Early pregnancy: • Later stages of pregnancy:

not very turbid turbid

• Used to evaluate premature rupture of membranes

Fern test

• Presence of '______on a________: positive screen for AF

fern-like' crystals dried vaginal fluid

DIFFERENTIATION FROM MATERNAL URINE •Amniotic fluid normally contains____ and_____ • Amniotic fluid has _____ and____levels equal to plasma

glucose and protein urea and creatinine

• Urine urea and creatinine levels are________ greater than plasma

50-100 times greater

• Creatinine comparison is challenging at _____ weeks of gestation

≥ 37 weeks

CHEMICAL EXAMINATION •_________ (now rarely performed)

FETAL LUNG MATURITY TESTS

•TESTS FOR FETAL DISTRESS (4)

• HEMOLYTIC DISEASE OF THE NEWBORN/AMNIOTIC FLUID BILIRUBIN • NEURAL TUBE DEFECTS • GENETIC TESTING (e.g., trisomy 21, 18, 13; family history) • FETAL INFECTIONS (TORCH complex)

A common cause of death in newborns due to ***insufficient surfactant production*** at the alveolar surfaces

• Respiratory distress syndrome:

• To assess if the fetus can survive outside of the uterus in cases of anticipated premature delivery

FETAL LUNG MATURITY TESTS

SURFACTANTS •90%______, 10%____

phospholipids; protein

Surfactants • Packaged into storage granules called_______, secreted by_____

lamellar bodies type 2 pneumocytes

•______release surfactants into the alveolar air space

Lamellar bodies

• keep the alveoli from collapsing by reducing the surface tension during breathing

Surfactants

FETAL LUNG MATURITY TESTS (5)

• Lecithin/sphingomyelin ratio • Phosphatidylglycerol • Foam stability index • Lamellar body count • Fluorescence polarization assay

reference method FETAL LUNG MATURITY TESTS

Lecithin/sphingomyelin ratio:

obsolete test FETAL LUNG MATURITY TESTS

Fluorescence polarization assay

major pulmonary surfactant

Lecithin

• ____weeks: ____ increases;_____ remains constant or decreases (produced at about 26 weeks)

34-36 lecithin sphingomyelin

L/S ratio • ______ : immature lungs • ______: fetal lung maturity • Measured using_____ and there should be no blood or meconium contamination

< 2.0 > or equal to 2.0 TLC

L/S Ratio Measured using____ and there should be no ___ or ____contamination

TLC blood or meconium

• A phospholipid that enhances the spread of surfactants across the alveolar surface

PHOSPHATIDYLGLYCEROL

PHOSPHATIDYLGLYCEROL • Not detectable until ____gestation

35 weeks

PHOSPHATIDYLGLYCEROL • Use TLC or agglutination slide test •________: contains anti-PG antibodies • Reporting:______

Amniostat-FLM negative, low positive, and high positive

• Also known as the 'shake test'

FOAM STABILITY INDEX

• ONLY A SCREENING TEST!

FOAM STABILITY INDEX

• Also known as the 'shake test'

FOAM STABILITY INDEX

•_____+_______, then shake for ______= production of foam and bubbles that remain stable for______ after shaking

Amniotic fluid + 95% ethanol 15 seconds 15 minutes

• Presence of foam: sufficient amount of______

phospholipids

FOAM STABILITY INDEX • Falsely mature results: if the AF is…..

contaminated with blood or meconium

FOAM STABILITY INDEX • Note: • A '_____' result on a contaminated specimen has no value • An '_____' result on a contaminated specimen is clinically useful

mature immature

• Storage of pulmonary surfactants

LAMELLAR BODY COUNT

LAMELLAR BODY COUNT • The number of lamellar bodies in AF correlates with the number of______ present in the lungs • Counted via the platelet channels of automated hematology analyzers

phospholipids

• Advantages: low volume needed (0.5 ml), short TAT, low cost • Fetal lung maturity: > 50,000/microliter in an uncentrifuged sample

Lamellar body count

Lamellar body count • Advantages:________ • Fetal lung maturity:_________

low volume needed (0.5 ml), short TAT, low cost > 50,000/microliter in an uncentrifuged sample

AMNIOTIC FLUID BILIRUBIN • Oldest routinely performed test on AF (for fetal anemia due to HDFN) • Measured using ______ • The optical density of the fluid is measured in intervals between_____ and______

spectrophotometry 350 nm and 580 nm

AMNIOTIC FLUID BILIRUBIN • Highest OD at_____ and decreases linearly to______: normal • If bilirubin is present, a rise in OD is seen at 450 nm (wavelength of maximum bilirubin absorption) • The difference between the OD of the baseline and the OD at 450 nm is the AF bilirubin concentration (also known as A450)

365 nm 550 nm

• are followed by measurement of amniotic acetylcholinesterase

Elevated results

• Reported in terms of multiples of the median (MoM) • Median is the laboratory's reference level for a given week of gestation • A fetus produces maximal AFP between 12-15 weeks and then its levels decline • A value greater than or equal to 2x the median value is considered abnormal

NEURAL TUBE DEFECT Detected by measuring… • If increased in both maternal circulation and amniotic fluid, it is indicative of NTDs like anencephaly and spina bifida (conditions when the skin fails to close over the neural tissue)

maternal serum alpha-fetoprotein (AFP)

• Detected by measuring maternal serum alpha-fetoprotein (AFP)

NEURAL TUBE DEFECT

NEURAL TUBE DEFECT • Detected by measuring maternal serum alpha-fetoprotein (AFP) • If increased in both maternal circulation and amniotic fluid, it is indicative of NTDs like_____ and _____ (conditions when the skin fails to close over the neural tissue)

anencephaly and spina bifida

NTDs • Reported in terms of______ • Median is the laboratory's reference level for a given week of gestation

multiples of the median (MoM)

• A fetus produces maximal AFP between ______ weeks and then its levels decline • A value ______the median value is considered abnormal

12-15 greater than or equal to 2x

NTDs - AFP • Elevated results are followed by measurement of…

amniotic acetylcholinesterase

Amniotic Fluid Flashcards

(74 cards)