11/05 - Prenatal Diagnosis Flashcards
Prenatal Diagnosis
Screening:
- For low risk patients
- Low financial cost
- Low procedure-related risk
- Positive test LEADS to diagnostic test
Diagnosis:
- 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
Screening:
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)
Diagnosis:
1) Amniocentesis
2) Chorionic Villus sampling
3) Cordocentesis
4) Pre-implantation Genetic Diagnosis (PGD)
Prenatal Diagnosis Indications
Pre-pregnancy:
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
