Prenatal Flashcards
(28 cards)
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
