genetic prenatal screening Flashcards
trisomy 21
down syndrome
trisomy 18
edward syndrome
trisomy 13
patau syndrome
risk factors for chromosomal abnormalities
advance maternal age (>35), previous pregnancy affected by chromosomal abnormalities, history of early pregnancy loss, advance paternal age >50, ethnicity
sickle cell
AA MC, increase risk of HTN and DVTs in pregnancy, miscarriage and low birth weight
a/b thalassemia
mediterranean (beta), asian origin (a)
tay-sachs disease
Ashkenazi Jewish, both parents must carry mutated gene
CF
caucasians of northern europe descent
Huntington’s disease
replication error
down syndrome complications
increase incidence of respiratory infections and leukemia
trisomy 16
the lethal anomaly occurs frequently in 1st trimester spontaneous abortion
what is a common congenital anomalies
neural tube defects
2nd most common major congenital abnormality in US
neural tube defects
which type of neural tube defect is most common
myelomeningocele
which type of neural tube defect is most lethal
anencephaly
what is the test of choice for neural tube defects
US
when is maternal serum screening ideally performed
16-22 weeks
2 key test for neural tube defects
folic acid and maternal serum and US screening
what does ACOG states
high quality 2nd trimester fetal anatomy US is an appropriate testing for NTD 18-22 weeks
when does visit occur for the 1st trimester
every 4 weeks until 28th weeks
how often is the visit for 3rd trimester
visit every 2 weeks until 36 weeks and then >36 weeks weekly
what screening is recommended in the 1st trimester
10-13 weeks of gestation
- assessment of cell free DNA/NIPTS
-US for nuchal translucency or biochemical markers
cell free DNA
looks for any abnormalities in the chromosome, if + then so an invasive diagnostic testing
what does serum markers assess for
all the trisomy disorders
PPAP-A
protein produced by the placenta needed for implantation process
decrease in PPAP-A in the 1st trimester indicates
Down syndrome
Beta-hCG that indicates an abnormalities
2x as high in pregnancy with Down syndrome
which US is preferred in the 1st trimester
transvaginal
when can the fluid in the fetal neck be seen and what it is called
nuchal translucency, seen in 10-14 weeks
what is abnormal nuchal translucency
more fluid in normal indicates abnormalities (trisomy)
what is included in the 2nd trimester screenings
triple screen/quad screenings, 2nd trimester US, NTD screening
what does 2nd trimester US look for
cardiac abnormalities, US markers, NTD
what is included in the 3rd trimester screenings
glucose challenge test, group B strep, Hgb/Hct, antibodies in Rh negative patients, STI, US if fetal growth restriction is considered
when do you conduct the glucose test
24-28 weeks
if the glucose challenge test is abnormal what other test needs to be done
glucose tolerance test
when do you perform the strep b test
36-37+6 days
what treatment can be given if the mother has strep B
PCN, if allergic then clindamycin
what can cause erythoblastosis fetalis
when a Rh - mom with Rh+ fetus blood mixes
what other times can a mom produce the abs for Rh
miscarriage, ectopic pregnancy, induced abortion
what is alloimmunization
formation of maternal antibodies
when do you screen for Rh
1st prenatal visit and again at 28 weeks
is Rho gam/Rh immunoglobulin helpful if you already produced the antibody for Rh
No
when do you administer the Rhlg
28th weeks and within 72 hours after delivery
what can trigger a maternal immune response
childbirth, delivery of placenta, ectopic pregnancy, abdominal trauma, amniocentesis
if the patient already has the antibodies what can you do
assess titers
how often do you assess titers for Rh
monthly until 24 weeks and then every two weeks
what happens if the titer remains low
delivery can occur at term
when do you start assessing fetal wellbeing in mother with Anti-D antibody
18 weeks
what is the definitive approach in diagnosing fetal anemia and acidosis
fetal blood sampling by cordocentesis
what happens if the fetal hct is <30%
intrauterine fetal transfusion with type o, RhD-
when should labor be induced if there is a concern for hemolysis
37 weeks
when is chorionic villus sampling performed
10-13 weeks
what sample does chronic villus sampling get
placenta
CI for chorionic villus sampling
maternal alloimmunization or IUD is in situ
when is amniocentesis performed
15-20 weeks
what is the accuracy of amniocentesis
> 99%
risk associated with amniocentesis
early amniocentesis(11-13 weeks) has a higher rate of pregnancy loss and complications
cordocentesis/ percutaneous umbilical blood sampling
needle is advanced into the umbilical vein under US guidance
when is cordocentesis performed
> 20 weeks
when are fetal assessments done
32-34 weeks
what is used to assess fetal growth
fundal heights and US
when is non stress test performed
32 weeks
what is considered reactive
> 2 HR accelerations occur in a 20 minute period
nonreactive
not enough acceleration occur in a 40 min period
what is a normal fetal HR in uterine contraction
3-5 contractions in 10 minute window, each lasting 30-40 sec
when is contraction stress test performed
34 weeks
what is used for contraction stress test (equipment)
tocodynamometer and fetal HR transducer
what is a positive test in CST
decrease in fetal HR during contraction or deceleration
what does late deceleration indicate
ueteroplacental insufficiency
what does early deceleration mean
pressure on fetal head from birth canal
variable deceleration indicate
transient umbilical cord compression
when is fetal scape sampling performed
during active labor and it is performed if fetal HR monitoring does not provide enough info
what test is performed give
1) non reactive NST
2) + CST
BPP
what does biophysical profile (BPP) entail
monitor fetal HR like NST + US
what score of BPP is reassuring
8-10
what is inconclusive in BPP
6
when is further testing need on a BPP score
<4
what does doppler US of umbilical artery assess
resistance to blood flow to placenta
when does fetal lung fully develop
36 weeks
what is the delivery averages for twins
35
average delivery time for triplets
32
risk factors for having twins
fertility treatments, advance maternal age, FH of twins
diamniotic/dichorionic
2 placenta, 2 amnios, 2 chorions or 1 fused placenta, 2 amnions, 2 chorions
diagnostic/monochorionic
1 placenta, 2 amnios, 1 chorion
Monoamniotic/monochorionic
1 placenta, 1 amnion, 1 chorion
conjoined twins
division after the 12th day is incomplete
