11/05 - Prenatal Diagnosis Flashcards Preview

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Prenatal Diagnosis

- For low risk patients
- Low financial cost
- Low procedure-related risk
- Positive test LEADS to diagnostic test

- For patients at increased risk
- May have higher financial cost
- Higher procedure-related risk
- Positive test considered definitive


2014 Prenatal Diagnosis Screening and Diagnosis steps

1) Combined First Trimester (studies skin on back of neck and combine that with biomarkers in blood test on Mom)
2) Integrated/Sequential/Contingent
3) Second Trimester Multiple Marker ("Quad")
4) Ultrasound
5) NIPT (Cell-free DNA; blood test on mom)

1) Amniocentesis
2) Chorionic Villus sampling
3) Cordocentesis
4) Pre-implantation Genetic Diagnosis (PGD)


Prenatal Diagnosis Indications

1) Maternal age >35 at due date
2) Previous child with autosomal trisomy
3) Parental structural chromosomal abnormality
4) Family history of a diagnosable genetic disorder
5) Previous child (or patient or spouse) with NTD (*not CVS)

During Pregnancy:
1) Abnormal screening test
- First Trimester Screen
- Second Trimester Maternal Serum Screen
- Positive NIPT
2) Ultrasound findings associated with a diagnosable genetic disorder

Various non-genetic indications...Fetal lung maturity, infections, etc.

*All patients desiring definitive diagnosis should be offered it, after counseling


When is Amniocentesis done (time-wise)

Ideally between 15 - 22 weeks to allow all therapeutic options.

- COULD do it earlier but higher complication rates before 14 weeks.


Amniocentesis Technique

- In amniocentesis, a hollow needle is inserted through the mother's abdomen into the uterus, and amniotic fluid is drawn for analysis


When are results available for amniocentesis?

- Less than 2 weeks after procedure
- Preliminary or FISH results in 24-48 hours


Risks of Amniocentesis

- 0.1 - 1.0% procedure related risk
Somewhere between 1/100 and 1/1000 losses


Neural Tube Defect Diagnosis in Amniocentesis

- Measurement of alpha fetoprotein
- Measurement of acetyl cholinsterase
- Efficacy of Ultrasound


Chorionic Villus Sampling (CVS) Advantages

- Earlier diagnosis
- Patient privacy (for those patients that might consider termination, easier if not everyone knows she's pregnant)
- Quicker results
- Psychological and emotional attachments
- Safer pregnancy termination


Chorionic Villus Sampling (CVS) Disadvantages

- Earlier procedure (nature may have taken care of this anyways)
- Lack of AFP Information
- Placental Mosaicism
- Higher pregnancy loss rate
- Limb reduction abnormalities


1983 History of CVS (big one)

- Report of trisomy 21 at 11 weeks, within 5 hours using ultrasound guidance and a flexible catheter


When do you do CVS?

10-13 weeks


When are results available for CVS?

results pretty quickly by looking at cells that are actively dividing and can get some information pretty fast


Procedure related risks of CVS

- 0.6-0.8% greater procedure related risk than amniocentesis

- Some more recent studies suggest that CVS is no more risky than amniocentesis


Limb Reduction Abnormalities

- Tapered fingers or toes or missing tips of fingers or toes.. Some clusters of cases happened in Europe and US when first introduced.
- Increased risk at <10 weeks
- Increased risk in programs with higher loss rates



- Percutaneous Umbilical Blood Sampling

Diagnostic (Previously, Rapid karyotype)
- Fetal blood: hematocrit
- Platelets
- Infection

- Transfusion
- Drugs


When do you do a cordocentesis?

- 18-20 weeks


Risks of Cordocentesis

Between 1-2% of increased loss rate