Amniotic Fluid Analysis
amniotic fluid
protects fetus while enabling movement; produced by amnion and placenta initially then by fetus (swallowing, respiration, and urination)
amniocentesis
transabdominally or vaginally with simultaneous ultrasound examination to collect amniotic fluid
diagnosis of genetic and congenital disorders
amniotic fluid collected early in gestation (15-18 weeks)
fetal lung maturity assessment
amniotic fluid collected at 32-42 weeks
estimate and monitor fetal distress
reason to collect amniotic fluid
aseptic technique
use of long sterile needle to collect 1-20mL of fluid into syringes and transferred into sterile plastic containers; should be protected from light and transported to lab immediately
glucose and protein present, creatinine similar to plasma, no urea
how to differentiate amniotic fluid from urine
urea or creatinine
best indicators to differentiate amniotic fluid from urine
colorless or pale yellow, somewhat turbid
normal appearance of amniotic fluid
bilirubin
gives amniotic fluid yellow or amber color
meconium
gives amniotic fluid green color
blood or hgb
gives amniotic fluid pale pink to red color
early pregnancy
little particulate matter present
late pregnancy
more tubidity due to increased fetal cells, hair, and vernix in fluid
pulmonary system
one of the last organ systems to mature
32 weeks
produces no testing value for chemical exam of fetal lung maturity indicating complete immaturity at that stage
respiratory distress syndrome
most common cause of death in newborn; results from insufficient production of surfactant in newborn's lungs
results of FLM and gestational age
how probability of respiratory distress syndrome is determined
lecithin/sphingomyelin (L/S) ratio
used to determine maturity of fetal lungs
phospholipids
required in fetal lungs to decrease surface tension (surfactants)
lectithin
major pulmonary surfactant
sphingomyelin
phospholipid in cell membranes; role yet to be established
34-36 weeks
lecithin increases and sphingomyelin stays constant or decreases
greater than or equal to 2.0
L/S ratio that indicates maturity of fetal lungs
phosphatidyl glycerol (PG)
not detectable until 35 weeks gestation; positive is very specific, but many false negatives
lemellar body counts
pulmonary surfactants sotred in lamellar bodies; use platelet automation to measure
greater than 50,000 per microliter
lamellar body count indicated FLM
amniotic fluid bilirubin
normally undetectable in amniotic fluid; correlates with severity of hemolysis; causes absorbance peak at 450 nm; bloody or meconium contaminated specimens unacceptable; must be protected from light
queenan chart
used to evaluate severity of hemolytic disease between 14 and 40 weeks gestation; divided into four zones indicating the severity of hemolysis