Prenatal Flashcards
Diagnostic techniques (3)
Chorionic villus sampling Amniocentesis Cordocentesis (PUBS)
Chorionic villus sampling
- can be performed transcervical or transabdominal
- performed 11-13 weeks
- problems: placental mosaicism (1-2%)
Amniocentesis
- performed >15 weeks
- can directly measure AFP and acetyl cholinesterase
- Risk of miscarriage = 1/1000
- Takes amniotic fluid; FISH results in 48 hours, Karyotype in ~2 weeks
Cordocentesis (percutaneous umbilical blood sampling - PUBS)
- needle inserted into fetal umbilical cord
- performed >18-20 weeks
- diagnoses fetal blood: hematocrit, platelets, infection
- therapeutic: transfusion, drugs
Screening techniques (5)
- First Trimester Screening
- Integrated/Sequential Screening
- Second trimester multiple marker screening
- Ultrasound
- NIPT
First Trimester Screening
- tests for Tri 18 and Tri 21
- performed 11-14 weeks
- NT measurement via u/s
- hCG and PAPP-A measurement
- risk adjustment
- Tri 18; Tri 21 risk flagged if greater than 1/270
Quad Screening
- Performed 16-22 weeks
- blood test measuring hCG, AFP, eU3 and inhibin A
- risk adjustment
- Tri 18, Tri 21 and open NTD
- Tri 21 risk flagged if greater than 1/270
NIPT
- performed anytime after 10 weeks
- blood test
- detects Tri 13, Tri 18, Tri 21 and XY
- can also detect Tri 16, Tri 22 and 7 microdeletions
- can pick up placental mosaicism
Ultrasound
- level 2 anatomy scan performed at 18-20 weeks
- can detect open NTD, Tri 21, Tri 13 and Tri 18
Integrated/Sequential/Combined Screening
-combines first trimester screening and quad screening for more accurate results
High risk pregnancy (features/qualifications)
- over 35 at delivery
- abnormal FTS/maternal serum screen
- abnormal ultrasound finding
- personal/family history of aneuploidy
IDDM (Insulin-Dependent Diabetes Mellitus) marker levels
- have lower MSAFP values than non-IDDM
- higher incidence of open NTDs
African American marker levels
- have a higher MSAFP concentration
- lower incidence of open NTDs
Reasons for elevated MSAFP
- underestimate gestational age
- multiple pregnancy
- open NTDs
- abdominal wall defect
- fetal and maternal blood mixed
- unexplained
Indications to test Amniotic fluid AFP and Acetylcholinesterase
- AFAFP >2.00 MoM
- patient at increased risk for an open NTD based on family history
- patient with IDDM
- patient with elevated MSAFP
- patient on valproic acid or tegretol
Down syndrome (marker pattern)
- increased hCG
- decreased AFP
- decreased uE3
- decreased PAPP-A
- increased NT
Trisomy 18 ultrasound findings
- u/s detects ~80% of fetuses with Tri 18
- IUGR
- heart defect
- strawberry shaped calvarium
- clenched fist
- rockerbottom feet
- micrognathia
- cleft lip +/- cleft palate
- omphalocele (25% of cases)
- diaphragmatic hernia
- NTD
- cystic hygroma
- polyhydramnios
- choroid plexus cysts
choroid plexus cysts
- cysts in the choroid plexus of the brain
- finding in 1% of normal fetuses at 16-24 weeks
- 90% resolve by 26-28 weeks
Men over 45
-increased risk for new dominant mutations (cannot be tested for)
Options for families with known conditions or abnormal test results (future pregnancies)
- PGD
- egg donation
- sperm donation
- adoption
Risk of Down Syndrome with a carrier mother of a Robertsonian Translocation (13;21, 14;21, 15;21, or 21;22)
10 - 15 % risk of a baby with translocation Down syndrome
Risk of Trisomy 13 with a carrier mother of a Robertsonian Translocation (13;14, 13;15, 13;21, or 13;22)
1% chance of having a baby with trisomy 13
Risk of a chromosomal abnormality in baby of a carrier mother of a Robertsonian translocation (14;15, 14;22, or 15;22)
Almost certainly no risk of having a baby with a trisomy, but possible risk of miscarriage or UPD.
Father with any Robertsonian translocation combination
Low risk, below 1%, of any child being affected
Same-chromosome translocation (Robertsonian)
- There is a group of carriers whose translocation chromosome consists of the two long arms of the same chromosome - 13;13, 14;14, 15;15, 21;21, or 22;22
- These carriers will always produce eggs or sperm with unbalanced chromosomes - either with two copies of the chromosome or none
What is the most common Robertsonian translocation?
13;14 (approximately 1 : 1,300 humans are a carrier)
(long arms of 13 and 14)
1 in ____ people are Robertsonian carriers
1000
What is an increased nuchal fold associated with?
Down Syndrome (Nuchal TRANSLUCENCY is associated with congenital heart defects as well, but nuchal FOLDS are not)
