Maternal Testing And Screening Flashcards
What timeframe is classified as 1st trimester screening? 2
- 11weeks 3 days
- 13 weeks 6 days
When is the 2nd trimester detailed anatomy scan?
18-20 weeks
When is dating done?
1st trimester
When do we do the growth and fetal wellbeing scans? What are some examples?2
As needed
1. Fetal assessment scan (FAS)
2. BPP and biometry and doppler
What are triple screen/ quad screen test?
Maternal blood test
What are some additional tests done outside of the 1st and 2nd trimester tests? 6
- Triple screen/ quad
- Non invasive prenatal testing
- Chorionic vili sampling
- Amniocentesis
- Percutaneous umbilical blood sample
- Fluorescence in Situ hybridization (FISH)
When is triple screen tests done?
16 weeks
What do we assess with triple screen?
- Maternal serum alpha feta protein
- Unconjugated estriol
- Beta hCG
What does the triple screen help use detect?
- Trisomy 21
- Trisomy 18
- other chromosomal abnormalities
What is the detection rates of triple screen?
~70%
Where is MS- AFP produced? 4
Mainly in the fetal liver also found in
1. Yolk sac
2. GI tract
3. Kidney
4. Placenta
AFP crosses the fetal placenta into what?
Maternal circulation
When does the MS-AFP levels rise?
About 14-20 weeks
Why would we have abnormal levels for MS AGP? 3
- Wrong date
- multiples
- Fetal abnormality
What is the MS-AFP for athletic women?
Increased MS- AFP
What does abruptions cause in terms of MS-AFP?
Increase it if enough fetal and maternal blood mix
What is a pro and con for MS-AFP?
It is sensitive but not specific
If conditions is MS- AFP is decreased it is related to what? 2
- Trisomy 21
- Trisomy 18
If MS-AFP is increased it is related to what? 7
- Open neural tune defect
- Gastroschisis
- GI obstruction
- Cystic hygroma
- RH sensitivity
- Placental abnormality
- Fetal death
Beta HCG is produced by what?
Trophoblasts which become the placenta
If beta hCG is increased what does it mean? 4
- Multiples in pregnancy
- Molar pregnancy
- Wrong dates
- Trisomy 21
If beta hCG is low what does it mean?
Trisomy 18
What produces unconjugated estriol?
Fetal adrenal glands and liver produce and synthesize a hormone that travels to the placenta which deconjugates it to estriol
Fetal malformations disrupts the normal process resulting in what?
Unconjugated estriol in the maternal blood
Decreased levels of unconjugated estriol are a marker for what? 2
T21 and T18
What do we look for in a quad screen?
Triple screen + Hormone Inhibin A
What produces inhibin A?
The baby and the placenta
Increased levels of inhibin A suggest what?
T21
According to AHS those that have inhibin A, we will find what? 3
- Neural tube defects 80% of the time
- Anencephaly 95% of the time
- Down syndromes 81% of the time
What is the 1st trimester screen test?
Early risk assessment
What does the 1st trimester screen test combine? 3
- Nuchal translucency
- Blood test
- Maternal age
What chromosomal anomalies does the 1st trimester test screen for? 3
- T13
- T18
- T21
What is the detection rate for 1st trimester screen?
85-90%
What is the false positive rate for T21, in the 1st trimester scan?
5%
What is the 1st trimester screen positive screen tests for T21, T18, T13?
- T21 = 1:300
- T18 = 1:1100
- T13 = 1:3000
In the 1st trimester, all trisomy’s are associated with what? 3
- Increased maternal age
- Increased fetal NT
- Decreased PAPP-A
In the 1st trimester scan, T21 B hCG levels are what?
Increased
For Trisomy 18 and 13 in the 1st trimester, Free B-hCG look are what?
Decreased
In the 1st trimester, when the presence of a nasal bone is assessed in the NT scan, the detection rate for T21 is what?
Increased to 95%
When would a nasal bone considered hypoplastic or absent? (value)
<2.5mm
What does NIPT stand for?
Non invasive prenatal testing
When is blood test taken for NIPT?
Maternal blood test taken at 10 weeks LMP
What do we test for during NIPT?
Testing the cell free DNA (cfDNA) in maternal plasma
How accurate is NIPT?
Extreme accurate >99% detection rate
False positive rate <0.1%
What are some maternal factors to consider for NIPT?
Increased maternal BMI can result in false negative result
Is NIPT considered a screening?
Yes
When is transcervical CVS performed?
Between 11- 12.5 weeks
How is transcervical CVS done? 2
- Catheter inserted through cervix to chorion frondosum
- With negative pressure from syringe, moving catheter back and forth to capture chorionic villi cells
What is a trans abdominal CVS?
Needle through abdomen to chorion frondosum
When would we perform a trans abdominal CVS?
Performed when placenta cannot be accessed by transcervical approach.
When can a trans abdominal approach be done? (weeks)
Beyond 12.5 weeks
What is the risk for trans abdominal CVS? (ratio and risk)
1/200 risk for spontaneous abortion
What is amniocentesis?
Amniotic fluid aspirated from the amniotic sac via a needle through the maternal abdomen
What are some risks of amniocentesis? 3
- Bleeding/ infection
- PROM/ Preterm labour
- Club feet
When would club feet be a risk factor for amniocentesis? 2 (weeks)
- When performed earlier than 16 weeks
- 16 weeks is now thought to be the optimum timing
What is the risk ratio for amniocentesis?
1/200 risk for spontaneous abortion
What do we note for amniocentesis? 5
- Number of fetuses and position
- Amniotic fluid volume
- Placental location
- Gestational age by biometry
- Limited anatomical survey -choroids, fetal hart, stomach, bladder, kidney, spine, bones
What must we do in terms of amniocentesis for heart rate?
Record heart rate with M-mode before and after procedure
What do we need to do for guided amniocentesis? 2
- Observe sterile techniques
- Open an amniocentesis tray and add items
What is added into amniocentesis tray?
- Needle = spinal needle - 16, 18, 20 gage
- 2 x 10cc syringes
- Cleaning solutions will be poured into vails
- Transducer supplies
What kind of cleaning solutions will be poured into vials for amniocentesis trays? 2
- Betadine - brown
- Alcohol - pink
What kind of transducer supplies do we add to the amniocentesis tray? 3
- BX guide
- Probe cover
- Sterile gel
What is the process for amniocentesis? 3
- Apply the Bx guide holder to the transducer and apply liberal amounts of gel to the transducer face
- Physician will offer the transducer cover to have you “drop” in the transducer
- Physician will clean and drape the operative site
Can the amniocentesis needle position be distorted?
Yes to due to refraction and reverberation artifacts
Why would physician scan to locate a pocket of amniotic fluid?
It is ideal to have no umbilical cord baby in pocket
How much cc’s of amniotic fluid is aspirated into each syringe?
10cc
Once the physician has the appropriate amount of fluids they will empty the contents how? Typically not how? Sometimes we do what? What must be on each vial?
- Into two vials
- Typically not on the sterile tray
- Sometimes we will assist by holding vials or they empty post procedure
- Patient identification information must be vials
What must we always do with the patient vials?
Confirm the patients ID on the vials with the patient or physician
What are the different types of amniocentesis? 4
- Cytogenetic amniocentesis
- O.D.D (Optical density determination)
- L/S amniocentesis
- Therapeutic
What is the most common reason to perform an amnio?
Cytogenetic amniocentesis to look for chromosomes
What is the reason to do O.D.D scans?
Rh sensitized fetuses
What is L/S amniocentesis?
Fetal lung maturity
Why would we do therapeutic amniocentesis?
For polyhydraminos
Amniotic fluid contains what kind of skin cells?
Fetal skin cells
The amniotic fluid is prepared how for analysis?
Cultured for analysis
What does cytogenetic amniocentesis do?
Fetal DNA is analyzed and biochemistry (AFP) tested
When can cytogenetic amniocentesis be performed?
Anytime after 11 weeks
Abnormalities detected at 18-20 week detailed scan will often require what?
Amniocentesis for chromosome analysis
Anomalies detected at any time will be offered what?
An amnio
When is cytogenetic amniocentesis routinely done?
16 weeks
What are the reasons to do a cytogenetic amniocentesis? 3
- Advanced maternal age
- Hx of congenital abnormalities in the previous pregnancy
- Family Hx in a direct relative to the fetus
How do we do Twin amniocentesis? 2
- First baby: After amniotic fluid aspired from the gestation sac Indigo carmine is injected into this sac
- If purple fluid is drawn out of the second baby we have the wrong sac
What is O.D.D?
Optical density determination
What does O.D.D. Measure?
Bilirubin levels in RH sensitized pregnancies
When is O.D.D. done?
Usually late 2nd semester or 3rd trimester
What is O.D.D. Sample?
Photosensitive sample
What is L/S sample stand for?
Lecithin/ Sphingomyelin ratio for lung maturity
What is Lecithin and sphringomylein?
Surfactants
What does lecithin and sphingomyelin do?
Responsible for the decrease in the surface tension in the alveoli of the lungs
What is the percentage of L/S ratio dispersed through the amniotic fluid?
Fairly equal in the amniotic fluid up to 33 weeks gestation
After the decrease of the surface tension in the alveoli of the lungs, what happens to Lecithin and sphingomyelin? 2
- Lecithin increases
- Sphingomyelin remains constant
If the L/S ratio is greater than two, what does this mean?
Lungs are considered mature
When is L/S ratio performed?
In 3rd trimester
Why is L/S ratio done?
When elective early delivery or repeat C-section is being offered
How common is L/S ratio?
Rarely performed now
What can therapeutic amniocentesis be done for? 3
- Polyhydraminos
- Twin to twin transfusion
- Hydrops
When would we do therapeutic amniocentesis? 3
- Mother is not able to tolerate pressure
- Enlarged uterus presses on abdominal contents
- Can cause SOB
When do we do Therapeutic amniocentesis?
As needed because fluid will reaccumulate within days
In terms of CVS vs amniocentesis, which obtains more DNA?
CVS
In terms of CVS vs amniocentesis, which one gets faster results?
Amniocentesis
What does PUBS stand for?
Percutaneous umbilical blood sampling
What is PUBS also know as?
Cordocentesis
How is PUBS performed?
Ultrasound guided needle into the umbilical cord ~1cm from insertion into placenta
What do we sample with PUBS?
Umbilical vein rather than artery
What is done prior to PUBS? 5
Pre-scan
1. FHR
2. Fetal position
3. AFI
4. Placental location
5. Placental cord insertion
How much blood is taken during PUBS during 2nd trimester?
Up to 4mls
How much blood is taken during PUBS during 3rd trimester
Up to 6ml of blood
What do we need to check 10 min post PUBS procedure?
Bleeding
What do we check 60 min post PUBS procedure?
FHR
What are some indications for PUBS testing? 6 (2)
- Fetal anemia in RH sensitization
- Fetal Blood transfusion
- Chromosomal analysis within 72 hours
- Fetal blood gas sampling in IUGR
- Fetal infection
- Treat fetal arrhythmias w/ medications
What are some risks of PUBS? 5
- Bleeding from puncture site s
- Infection
- Cord hematoma
- Rupture of membrane s
- Fetal loss (1%-5%)
What does FISH stand for?
Fluorescence in Situ hybridization
What does FISH look for?
How many copes are present for specific chromosome like 13, 18, 21, X and Y
What is a advantage of FISH?
It does not require all the steps needed as in cytogenetic karyotyping
What is a disadvantage of FISH?
No information on the structure of the chromosome
What is FISH performed on? 3
Fetal blood, amniotic fluid and/ or CVS
How fast do we get the results of FISH?
Very fast within 3-4 days
