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70 Cards in this Set
- Front
- Back
How is amniotic fluid collected?
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Amniocentesis
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Amniocentesis
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Performed between 14-38 weeks, 15-30 mL collected Initial AF is an ultrafiltrate of mom’s plasma and has plasma-type values for electrolytes, urea, creatinine, etc.
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Why does amniotic fluid need to be kept from light?
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To maintain bilirubin levels
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What temperature does an amniotic fluid sample need to be kept?
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27-35 degrees for cell analysis
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What test of the amniotic fluid requires the sample to be put on ice?
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Fetal lung maturity testing because cell metabolism can change sample pH.
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What color is amniotic fluid during the first and second trimester?
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Yellowish
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What color is the amniotic fluid during the THIRD trimester?
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Colorless, turbid because of surfactant
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During maturation, the baby alters amniotic fluid. (T/F)
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True
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What analytes are increased by the baby urinating?
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Urea, uric acid, creatinine
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What analytes are increased by the baby breathing?
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Pulmonary lipids (lecithin, sphingomyelin, phosphatidylglycerol)
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What else is introduced into the amniotic fluid by the baby?
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Protein form fetal GI tract, skin, and respiratory tract
Hormones (GH, insulin, FSH, LH, ACG, ACTH, Esterdiol, T4 |
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What is the final volume at term?
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300 - 1500mL
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Oligohydramnios
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Low volume. Saline can be added
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Polyhydraminos
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Excessive volume
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What another name for lecithin?
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Dipalmitoyl phosphatidylcholine
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How do we test for HDN?
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Intrauterine hemolysis monitored by AF A450
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What is another name for HDN?
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Erythroblastosis fetalis
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What is HDN?
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ABO incompatability of (usually) Rh negative mother and Rh positive fetus, leading to antibody response and RBC hemolysis = bilirubin in amniotic fluid
Fetal anemia stimulates erythropoisis leading to elevated unconjugated bilirubin due to decreased conjugation by liver. Unconjugated bilirubin can cross the blood/brain barrier. Unconjugated bili (fat soluble) is toxic to CNS and causes kernicterus. |
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What are the symptoms of HDN at birth?
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Anemia and kernicterus
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What are the diagnosing criteria for kernicterus?
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> 15 mg/dL tot. bilirubin
> 10 mg/dL for 2 weeks |
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How do we measure bilirubin levels?
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Direct spectrophotometry. Measure bilirubin and its breakdown products from 400 to 700 nm,
draw a baseline and determine elevated absorbance at 450 nm. |
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What are some interfering substances when measuring bilirubin.
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hemolysis (visible in sample and Hb peak), meconium (baby's feces), vernix (white gooey substances in AF, remove by centrifugation)
Reject hemolyzed and meconium samples |
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At which zone on a Liley chart is intervention necessary?
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Zone 3. Either intraurterine transfusion or delivery (Check lung maturity first)
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What is surfactant and where is it secreted?
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Surfactant is a type of phospholipid, full of saturated fatty acids (phosphotidylcholine = lecithin, sphingomyelin, phosphotidylinositol). It is formed by type II pnemocytes and lines the alveolar epithelium.Surfactant maintains lung function by maintaining alveolar stability and reducing pressure needed to distend lungs (surface tension of alveolar wall)
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What are type I pneumocytes equipped for
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Gas exchange
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What are the components of surfactant?
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phosphotidylcholine = lecithin, sphingomyelin, phosphotidylinositol
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What is Respiratory Distress Syndrome (RDS) or hyaline membrane disease.
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Higher risk if delivery before 34 weeks.
Very small amount of lecithin and sphingomyelin Alveoli collapse upon exhaling due to lack of surfactant Collapse restricts gas exchange which causes respiratory acidosis and hypoxia |
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What is RDS caused by?
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Respiratory distress syndrome is caused by the inability of immature lungs to produce pulmonary surfactant, the lipid conjugate that reduces surface tension in the lungs and promotes inflation of the lungs.
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What can be done to prevent RDS?
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Cortisol can be given to delay birth when preterm labor is indicated. And trigger the maturation process of the lungs when administered between 30-33 weeks of gestation AND within a week of birth.
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What is Pre-eclampsia?
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Pre-eclampsia is a condition of pregnant women marked by water retention (with swelling particularly in the feet, legs and hands), high blood pressure and protein in the urine.
Eclampsia is when pre-eclampsia progresses to a grand mal seizure |
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What is a screening test for fetal lung maturity?
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Foam stability Index (FSI) or shake test
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How is the Foam stability test or shake test performed?
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Mix equal parts of amniotic fluid and methanol.
Amount of bubble correlates to the amount of surfactant in baby's lungs |
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What is a L/S ratio?
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Compare the amount of lecithin (L) to the amount of sphingomyelin (S) in amniotic fluid in order to determine whether the type II pneumocytes have begun to secrete surfactant.
Sphingomyelin has no surfactant activity and is used to correct for dilutional effect of the volume of amniotic fluid |
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In L/S ratio, if L/S > 2.0 and PG+
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low risk for RDS
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In L/S ratio, if L/S > 2.0 or PG+ (not both)
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Medium risk for RDS
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In L/S ratio, if L/S < 2.0 and PG-
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high risk for RDS (delivery should be delayed if possible)
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Diabetic mothers need > 2.5 and PG+ to be considered low risk. (T/F)
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True
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What is PG
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Qualitative immunoassay
> 2 mg/L indicates low risk for RDS Not a ratio, therefore does not correct for large or small volume of AF |
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What is Amniotic surfactant to Albumin ratio or Fetal lung maturity test (FLMT)?
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The assay is performed on a special fluorescence polarization instrument
"Mature fetal lungs" are indicated by values greater than 50 mg surfactant per gram of albumin |
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What are lamellar bodies?
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Lamellar bodies are the storage form of surfactant and are similar in size to normal platelets.
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How is a Lamellar Body Count performed?
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They can be counted on a automated cell counter
A count of these bodies estimates the amount of surfactant present A lamellar body count >30,000/μl is highly predictive of pulmonary maturity, while a count <10,000/μl suggests a risk for Respiratory Distress Syndrome Lamellar body count methods are faster and less technique dependent than traditional phospholipids analysis |
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What technique is used to measure bilirubin levels in amniotic fluid?
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Spectophotometry
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What technique is used to measure the surfactant to albumin ratio?
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Fluorescence polarization
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What technique is used to measure the L:S ratio?
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Chromatography
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Neural tube forms ____________ and _____________ during development
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brain and spinal cord
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What is spina bifida?
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A condition where the neural tubes do not close (tissue does not cover spinal cord) and the baby's spinal fluid seeps into AF and AF gets absorbed into mom's plasma
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What is encephalocele?
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a protrusion of brain through an abnormal opening
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What is anencepha?
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a condition in which the fetus does not develop a cerebrum
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What does the baby's liver make In all the neural tube defects instead of albumin longer than it should?
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Alpha fetal protein measured in mom's plasma by immunoassay. Increase result is preliminary indicator of open neural tube defect, must be followed by ultrasound and AFAFP. Ultrasound because AFP can be increased with multiple pregnancies.
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What is the most significant protein that is found in the second trimester fetus?
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AFP
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What is AFP and where is it produced?
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a transport protein produced by the fetal liver with a function similar to that of albumin
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What does AFP bind and transport?
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binds and transports substances that are not very water soluble such as steroid hormones, vitamins, lipids and bilirubin
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Where is AFP found?
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found in amniotic fluid and maternal circulation only in small amounts under normal circumstances due to its large molecular weight and inability to diffuse readily to maternal circulation from the feto-placental circulation
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In what conditions is AFP elevated?
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OPEN NEURAL TUBE DEFECTS, Trisomy 13, twins or other multiple gestations, underestimated gestational age
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In what conditions is AFP decreased?
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DOWN'S SYNDROM, Trisomy 18
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When is AFAFP measured?
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Between 15 and 21 weeks of pregnancy
<15th week – too little to accurately measure >21st week– normal range is too wide to detect accurately |
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How are the results reported in an AFP?
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Results reported in MOM (multiples of median = how many times normal)
Normal is <2.0 MOM unit |
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AFAFP is increased in ________% of ONTD cases.
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90%
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Folic acid can reduce the risk of ONTD. (T/F)
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True
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How do you calculate MoM units?
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Serum AFP / avg. of fetus' at that gestational age
If elevated, quad screen can be performed |
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What is Downs syndrome?
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Down syndrome is a congenital disorder of the autosomal chromosome 21 with either a trisomy or three copies of the long arm, or translocations of the long arm
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What are the lab markers for Down's syndrome?
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decreased MSAFP, decreased unconjugated estriol and increased chorionic gonadotropin levels. (Triple Screen) Add inhibin becomes quad screen.
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What is the definitive tst for Down's syndrome?
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fetal karyotyping
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What is Trisomy 18?
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Trisomy 18, an extra copy of chromosome 18, results in open neural tube defects, and death of the infant within a few months.
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What screen is used to determine whether or not the patient has trisomy 18?
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The triple screen of maternal serum provides the same type of abnormal results as does Down’s syndrome while fetal karyotyping is the definitive test and will differentiate trisomy 21 from 18
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Multiple pregnancies (twins) can result in nearly double the amount of alpha fetoprotein found in maternal circulation. (T/F)
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True
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Multiples of median (MoM) is a statistical application of the biochemical marker used to normalize values for reference ranges that change readily with age or other factors. (T/F)
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True
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What is the fetal fibronectin test?
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Test used to predict imminent delivery within the next few weeks. Fibronectin is a glue like protein used to hold baby in womb. protein breakdown before labor and release in uterus. indicative of imminent delivery (within 2 weeks)
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(TPQ) Decreased maternal AFP and increased hCG suggest high risk for what clinical condition?
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Down's syndrome
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(TPQ) what is the unit for AFP?
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MoM
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