CHAPTER 15: AMNIOTIC FLUID Flashcards
The constituents that are present in the fluid provide information about the metabolic processes taking place during—as well as the progress of—fetal maturation
Amniotic fluid
a membranous sac that surrounds the fetus where amniotic fluid is present
amnion
Cells composing the amnion
cuboidal cells
Functions of amniotic fluid (4)
1) Protective cushion for the fetus
2) Allow fetal movement
3) Stabilize temperature
4) Permit proper lung development
A volume of amniotic fluid greater than 1200 mL is called
Polyhydramnios
The volume of amniotic fluid less than 800 mL is termed
Oligohyramnios
During the 1st trimester, 35 mL of amniotic fluid is derived from _____________.
maternal circulation
Major contributor to the amniotic fluid volume after the 1st trimester.
Fetal urine
Indication of fetal distress and often associated with neural tube disorders.
Failure of the fetus to begin swallowing urine which results in excessive accumulation of amniotic fluid (polyhydramnios)
May be associated with
> congenital malformations
> premature rupture of amniotic membranes
> umbilical cord compression
resulting in decelerated heart rate and fetal death.
Oligohydramnios
The ultimate source of amniotic fluid water and solutes
placenta
Allow fetal cerebrospinal fluid to enter the amniotic fluid directly.
Neural Tube Defects
Two biochemical makers tested to detect Neural Tube Defects (NTDs)
Alpha-fetoprotein (screening)
Acetylcholinesterase (confirmatory)
Used to determine fetal age
amniotic fluid creatinine (>2.0mg/dL = 36 weeks/9months)
Differentiates amniotic fluid and maternal urine
Chemical analysis of creatinine, urea, glucose, and protein
*crea and urea - lower in amniotic, high in urine
Can differentiate amniotic fluid from urine and other body fluids used to evaluate premature rupture of the membranes
Fern test
Specimen for fern test
Vaginal fluid
Positive screen for amniotic fluid in fern test, where fern-like crystals appear are due to what content/s?
protein and sodium chloride
Amniotic fluid pH
7.1 to 7.3
A screening test used to determine the presence of amniotic fluid in vaginal secretions.
nitrazine test
A blue-colored strip indicating a pH greater than 6.0 in a nitrazine test suggests …
membranes have ruptured
Referred to as placental protein
Insulin-like growth factor binding protein -1 (IGFBP-1)
Recommended for cases of NTDs when screening blood tests, such as the maternal serum AFP test, are abnormal or to detect genetic disorders or to evaluate the health of the fetus
Amniocentesis
Note:
Amniocentensis - after 14th week of gestation
Fluid chromosome analysis - 16 weeks
Intrauterine growth retardation - end of 2nd trimester
Fetal distress and matury - Later in 3rd trimester
Max. volume of amniotic fluid collected in sterile syringes
30 mL (First 2/3mL = discarded)
Transport medium for fetal lung maturity test fluid
ice
Used to determine the source of the blood (maternal or fetal) for fetal hemoglobin
Kleihauer-Betke Test
Gives the fluid a yellow color and is indicative of red blood cell destruction resulting from HDFN.
bilirubin
Defined as a newborn’s first bowel
movement, a dark green, mucus-like material. It may be present in the amniotic fluid as a result of fetal distress.
Meconium
A very dark red-brown fluid is associated with
fetal death
Measures amniotic fluid bilirubin
spectriophotonetric analysis using serial dilution
Most common birth defects in the United States
Neural Tube Defects (NTDs)
Most frequent complication of early delivery and is the seventh most common cause of morbidity and mortality in the premature infant.
Fetal Lung Maturity
Keeps the alveoli from collapsing by decreasing surface tension and allows them to inflate with air more easily
Surfactant
Reference method to which tests of FLM are compared
Lecithin-sphingomyelin Ratio
Primary component of surfactant that make up the alveolar lining and account for alveolar stability
Lecithin
Indication when the L/S ratio reaches 2.0
Safe preterm delivery
A mechanical test used to measure the individuall lung-surface lipid concentrations
Foam or Shake Test
Composition of surfactant
90% phospholipids
10% protein
*packaged into layered storage granules called lamellar bodies
They are secreted by the type II pneumocytes of the fetal lung at about 24 weeks of gestation and are absorbed into the alveolar spaces to provide surfactant
Lamellar bodies
True or False.
Amniotic fluid specimens containing whole blood, meconium, and mucus should not be used
True
