11/05 - Prenatal Diagnosis

Question 1

Prenatal Diagnosis

Answer 1

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

Question 2

2014 Prenatal Diagnosis Screening and Diagnosis steps

Answer 2

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)

Question 3

Prenatal Diagnosis Indications

Answer 3

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

Question 4

When is Amniocentesis done (time-wise)

Answer 4

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

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

Question 5

Amniocentesis Technique

Answer 5

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

Question 6

When are results available for amniocentesis?

Answer 6

• Less than 2 weeks after procedure

- Preliminary or FISH results in 24-48 hours

Question 7

Risks of Amniocentesis

Answer 7

• 0.1 - 1.0% procedure related risk

Somewhere between 1/100 and 1/1000 losses

Question 8

Neural Tube Defect Diagnosis in Amniocentesis

Answer 8

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

Question 9

Chorionic Villus Sampling (CVS) Advantages

Answer 9

• 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

Question 10

Chorionic Villus Sampling (CVS) Disadvantages

Answer 10

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

Question 11

1983 History of CVS (big one)

Answer 11

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

Question 12

When do you do CVS?

Answer 12

10-13 weeks

Question 13

When are results available for CVS?

Answer 13

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

Question 14

Procedure related risks of CVS

Answer 14

• 0.6-0.8% greater procedure related risk than amniocentesis

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

Question 15

Limb Reduction Abnormalities

Answer 15

• 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

Question 16

Cordocentesis

Answer 16

• Percutaneous Umbilical Blood Sampling

Diagnostic (Previously, Rapid karyotype)

• Fetal blood: hematocrit
• Platelets
• Infection

Therapeutic:

• Transfusion
• Drugs

Question 17

When do you do a cordocentesis?

Answer 17

• 18-20 weeks

Question 18

Risks of Cordocentesis

Answer 18

Between 1-2% of increased loss rate