Pre and Neonatal Screening

Question 1

Types of screening (4)

Answer 1

1. Invasive prenatal diagnosis
2. Non-invasive prenatal diagnosis
3. Non-invasive prenatal screening
4. Newborn screening

Question 2

Amniocentesis

Answer 2

-amniotic fluid extracted trans abdominal at 16-20 weeks

Question 3

What signals a neural tube defect with amniocentesis?

Answer 3

High alpha-fetoprotein (AFP)

Question 4

In addition to neural tube defects, high levels of AFP can cause? (4)

Answer 4

1. Twinning
2. Fetal death
3. False positives if gestational age undetermined
4. Other fetal abnormalities

Question 5

What is chorionic villus sampling?

Answer 5

• Transcervical or transabdominal collection done between 10th and 13th week
• same general risk as amniocentesis

Question 6

Can CVS detect AFP levels?

Answer 6

No

Question 7

What is pre-implantation genetic diagnosis (PGD)?

Answer 7

• implant genetically sound embryo, discard the rest

- allows for selection of embryos before in vitro fertilization

Question 8

Methods of PGD

Answer 8

1. Blastomere biopsy (pre-compaction)

2. Blastocyst biopsy (trophoectoderm)

Question 9

What is the purpose of ultrasonography?

Answer 9

• To look for structural fetal abnormalities

- >13 weeks

Question 10

Why might someone get prenatal diagnosis? (6)

Answer 10

1. Previously, advanced maternal age
2. Genetic risk in family
3. Another child with de novo chromosomal abnormality
4. First-degree relative of someone with NTD
5. Prenatal screening suggests something is wrong
6. Termination decision/anxiety reduction

Question 11

What prenatal screening of maternal serum is done in 1st trimester? (2)

Answer 11

1. Pregnancy-associated plasma protein A (PAPP-A); lower in trisomies
2. Human chorionic gonadotropin (hCG); changed in trisomies

Question 12

What prenatal screening of maternal serum is done in 2nd trimester? (2)

Answer 12

1. Unconjugated estriol; lower in trisomies

2. Inhibin A; changed in trisomies

Question 13

Cell-free fetal DNA

Answer 13

• fetal DNA circulating in maternal blood
• 2-10% of cell free DNA in maternal blood is from placental trophoblasts

High-throughput sequencing

Question 14

Ways to screen/diagnose Down’s Syndrome

Answer 14

1. CVS/amnio: karyotype from material and look for trisomy 21
2. Maternal serum: PAPP-A low; HCG elevated; inhibit A elevated; unconjugated estriol low
3. Ultrasonography: widened unchallenged translucency

Question 15

History of newborn screening

Answer 15

1960s—test developed for PKU, established how to store blood on filter paper
2002–expanded testing,most states only tested for 4-6 disorders before
2011–all states test for at least 26 disorders
1 in 300 infants diagnosed

Question 16

Requirements for newborn panel (3)

Answer 16

1. Conditioned can be identified 24-48 hours after birth, when it cannot usually be detected by a doctor’s exam
2. Available test that is specific and sensitive for condition
3. Early detection, timely intervention, and effective treatment offer proven benefit

Question 17

Newborn screening examples (7)

Answer 17

1. Maple syrup urine disease
2. PKU
3. Congenital hypothyroidism
4. Beta-thalassemia major
5. Sickle cell anemia
6. Cystic fibrosis
7. Severe combined immunodeficiency (SCID)