URINALYSIS AND BODY FLUIDS (AMNIOTIC FLUID) LECTURE

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URINALYSIS AND BODY FLUIDS (AMNIOTIC
FLUID)LECTURE

• Dr. Essam H. Jiffri

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• Amniotic fluid is found in the membranous sac
  that surrounds the fetus and provides a cushion
  to protect the fetus

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Amniotic Fluid

• - The Fluid formed from the metabolism of fetal
  cells, transfer of water across the placental
  membrane, and, in later stage of development, by
  fetal urine.
• - By the time production of fetal urine occurs,
  the fetus begins swallowing the amniotic fluid in
  an amount approximately equal to the urine
  output.

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Amniotic Fluid

• - The buildup of amniotic fluid to a total volume
  of 500 to 2500 ml at term is produced primarily
  by increased cell metabolism and placental water
  exchanges.
• - In ability of the fetus to swallow is a
  critical sign and is indicated by an abnormal
  increase in amniotic fluid.

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Amniotic Fluid

• - Fluid for analysis obtained by needle
  aspiration into the amniotic sac, a procedure
  called amniocentesis.
• - The procedure is relatively safe and can be
  performed on an outpatient basis.

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Amniotic Fluid

• - Specimens should be protected from light.
• - Special precautions must be taken with
  specimens for cytogenetic analysis because cells
  in the fluid must be kept alive for culturing by
  the laboratory.

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Amniotic Fluid

• - Cytogenetic analysis has become an important
  predictor of birth defects.

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FETAL DISTRESS

• - Clinical analysis of amniotic fluid assesses
  both fetal well being and maturation.
• - Because amniotic fluid is a product of fetal
  metabolism, the constituents that are present in
  the fluid provide information about the metabolic
  processes taking place and the progress of fetal
  maturation.

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FETAL DISTRESS

• - The oldest routinely performed laboratory test
  on amniotic fluid evaluates the severity of the
  fetal anemia produced by hemolytic disease of the
  newborn.
• - Those infants are referred to as (R h babies).

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FETAL DISTRESS

• - The incidence of this disease has been
  decreasing rapidly since the development of
  methods to prevent anti-R h antibody production.
• - The destruction of fetal red blood cells by
  antibodies that are present in the maternal
  circulation results in the appearance of the red
  blood cell degradation product, bilirubin, in the
  amniotic fluid.

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FETAL DISTRESS

• - By measuring the amount of bilirubin present in
  the fluid, it is possible to determine the degree
  of hemolysis taking place and to assess the
  danger of this anemia presents to the fetus.
• In cases of premature or prolonged rupture of
  the amniotic membranes there is concern over
  possible infection of the mother and fetus.

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FETAL DISTRESS

• - Testing of the fluid with the leukocyte
  esterase reagent strip for the presence of white
  blood cells is shown to be a good indicator of
  infection and is more rapid and cost effective
  than Gram stains and cultures.

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FETAL MATURITY

• - Fetal distress, whether caused by hemolytic
  disease of the newborn or other conditions,
  forces the obstetrician to consider a preterm
  delivery, therefore, it becomes necessary to
  assess fetal maturity.
• - Respiratory distress is the most frequent
  complication of early delivery.

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FETAL MATURITY

• - Laboratory tests are performed to determine the
  overall fetal maturity.
• - The laboratory procedure routinely used to
  measure fetal lung maturity is the
• lecithin ratio (L/S ratio).
• - Lecithin is the primary component of the
  phospholipids that make up the majority of the
  alveolar lining and a count for alveolar
  stability.

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FETAL MATURITY

• - Lecithin is produced at a relatively low and
  constant rate until the 35th week of gestation,
  at which time a noticeable increase in its
  production occurs, resulting in the stabilization
  of the fetal lung alveoli.
• - Sphingomyelin is a lipid that is produced at a
  constant rate throughout fetal gestation
  therefore, it can serve as a control on which to
  base the rise in lecithin.

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FETAL MATURITY

• - Prior to 35 weeks of gestation, the L/S ratio
  is usually less than 1.6 and it will rise to 2.0
  or higher when lecithin production increases.
• - When the L/S ratio reaches 2.0 a preterm
  delivery is usually considered to be a relatively
  safe procedure.

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FETAL MATURITY

• - Measurement of lecithin and sphingomyelin is
  performed using thin-layer chromatography.
• - Absence of phosphatidylglycerol in the presence
  of a normal L/S ratio is seen in children of
  diabetic mothers

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FETAL MATURITY

• - At about 36 weeks of gestation, urine from the
  fetal kidney begins appearing in the amniotic
  fluid therefore, creatinine concentration above
  2.0 mg per dl indicates a fetal age of
  approximately 36 weeks.

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FETAL MATURITY

• - The measurement of alpha fetal protein levels
  and acetylcholinesterase activity is being used
  to provide early detection of neural tube
  disorders, such as spina bifida.

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Summary of the routine chemical tests performed
on amniotic fluid

• Tests for the Well-being and Maturity
• __________________________________________________
  ________
• Test Normal values at term
  Significance
• __________________________________________________
  ________
• Bilirubin scan 0.025 mg/dl Hemolytic
  disease of the newborn
• L/S ratio 2.0 Fetal lung maturity
• Phosphatidyl- Present Fetal lung maturity
• Glycerol
• Creatinine 1.3 4.0 mg/dl Fetal age
• Alpha fetal protein 4.0 mg/dl Neural tube
  disorders
• __________________________________________________
  ________