Prenatal Screening Part 1 Flashcards
What is the purpose of prenatal screening (maternal serum screening)?
to identify women at increased risk for an affected pregnancy (by non-invasive technology) and to maximize (prenatal) options available to them
What teratogens are associated with increased fetal risk for anomalies including NTD?
valproic acid, phenytoin, and other medications used to treat epilepsy (phenobarbital safer alternative)
maternal DM
folic acid antagonists being taken by mother
What are the possible etiologies of Down Syndrome?
95% Trisomy 21
3% translocation
2% mosaic trisomy 21
What features are associated with Down Syndrome?
moderate intellectual delay, characteristic facial features, 1/2 cardiac defects, hearing issues, leukemia, etc.
What features are associated with Edward’s Syndrome?
typically lethal
liveborns display profound mental retardation, severe IUGR, cardiac defects, malformed ears, micrognathia, etc
most die in first year of life
What 2nd trimester US findings are consistent with Edward’s Syndrome?
cardiac anomaly, omphalocele, neural tube defects, cystic hygroma (or increased NT), IUGR, clenched fists, rocker-bottom feet, etc.
Describe the indications of different levels of MSAFP.
HIGH 4 MoM- spina bifida 7 MoM- anencephaly 9 MoM- gastroschesis *note African Americans will have increased MSAFP LOW Down Syndrome
AFP is originally made in the _______, and after _____ weeks it is made in the _______.
yolk sac
12
fetal liver and GI
What does a positive acetylcholinesterase indicate?
an abdominal wall defect
When is acetylcholinesterase ordered?
if AFAFP is abnormal (>3 SD)
What are possible etiologies of elevated MSAFP?
incorrect pregnancy dating
multifetal pregnancy
fetal death/miscarriage
first trimester bleeding/placenta abnormalities
What are the most common etiologies of MSAFP (that should be in your DDx)?
open neural tube defects abdominal wall defects renal anomaly congenital nephrosis unexplained (when US does not reveal an etiology)
What could an unexplained elevated MSAFP indicate an increased risk for?
placental abruption
perinatal loss
low birth weight due to preterm labor and/or IUGR
other (preeclampsia, oligohydramnios, etc)
What is Estriol?
UE3
estrogen based hormone made in syncytial trophoplast from precursors originating in adrenals
increases with gestational age
What is hCG?
Human Chorionic Gonadotropin
pregnancy hormone glycoprotein with 2 subunits produced in placenta
decreases as gestational age increases
What is inhibin?
dimeric glycoprotein hormone produced in gonads and placental tissue but functional in pregnancy still being studied
seems to inhibit FSH
What is the pattern of serum analyte results consistent with NTD on second trimester screening?
HIGH AFP
What is the pattern of serum analyte results consistent with Trisomy 21 on second trimester screening?
LOW AFP
LOW UE3
HIGH hCG
HIGH Inhibin
What is the pattern of serum analyte results consistent with Trisomy 18 on second trimester screening?
LOW AFP
LOW UE3
LOW hCG
What is the pattern of serum analyte/US results consistent with Trisomy 21 on first trimester screening?
Large NT
HIGH b-hCG
LOW PAPP-A
What is the pattern of serum analyte/US results consistent with Trisomy 18 on first trimester screening?
Large NT
LOW b-hCG
LOW PAPP-A
What is the pattern of serum analyte/US results consistent with Trisomy 13 on first trimester screening/
Large NT
LOW b-hCG
LOW PAPP-A
What is a the quad screening?
AFP
UE3
hCG
Inhibin
What is the triple screening?
AFP
b-hCG
estriol
What is the combined screen?
triple screening (AFP, b-hCG, estriol) plus US (NT and crown-rump length)
What is the integrated screen?
quad screening (AFP, UE3, hCG, Inhibin) plus the combined screening (triple screening plus US) issued once both are completed
What is the sequential screen?
one report summarizing the risk issued after the first trimester followed by a revised report once second trimester screening completed
What is increased NT associated with?
increased aneuploidy
increased risk of cardiac anomalies and/or increased risk for other congenital anomalies
>/= 3.5mm associated with increased risk for rare genetic diseases including DeGeorge syndrome, Noonan’s syndrome, and increased risk for poor outcome (stillbirth, miscarriage, etc)
What biomarkers are indicative of increased risk for rarer conditions that are not always noted on lab reports?
LOW UE3 (second trimester)- Smith-Lemli-Opitz syndrome
LOW PAPP-A (first trimester)- Cornelia de Lange
very LOW or undeectable UE3 (second trimester)- Steroid Sulfatase Deficiency/ X-linked Ichthyosis
LOW UE32- Congenital Adrenal Hypoplasia
ALWAYS confirm _____ testing results with ______.
NIPS
CVS or amnio
Provide a summary of prenatal screening options by trimester.
First trimester- First trimester screening (combined US with PAPP-A and hCG) + NIPS
Second trimester- Second trimester screening + NIPS (if not already done) + anatomy US
Provide a summary of diagnostic options.
First trimester- chronic villus sampling
Second trimester- amniocentesis
When can CVS be performed?
between 10 and 14 weeks gestational age
When can amniocentesis be performed?
between 15 and 22 weeks gestational age
