Week 4 Fetal Assessment Flashcards
What is the Primary objective of prenatal screening and diagnosis?
to detect genetic d/o or abnormalities that could affect the woman, fetus, and newborn
Explain Screening vs Diagonistic testing
- Screening detects or IDs individuals who are at risk for an abnormality or disease to then be diagnosed
- Diagnostics precise test for a given condition
What is the major limitation of screening tests?
risk of false-negative and false-positive
What are the diagnostic testing options?
- Chorionic villus sampling
- Amniocentesis
- Preimplantation genetic diagnosis
What are the three categories of ultrasounds?
- Standard
- Limited
- Specialized
What all can an ultrasound tell you?
-Maternal anatomy (cervix, uterus, adnexa)
-Number of fetuses
-Biometry (fetal measurements, estimate gestational age, fetal weight, whether structures are abnormal or not)
–Survey of fetal anatomy
Fetal presentation
-Presence of fetal cardiac activity
-Placental location
-AF volume
What is a limited ultrasound?
provides information about a specific problem or concern that require further evaluation
What is a specialized ultrasound? When is it indicated?
(usually performed by specially trained staff such as MFM physician)
- Suspected or known fetal structural anomaly (gastroschisis)
- Suspected or known fetal genetic or chromosomal abnormality
- Hx of previous preg with anatomic, genetic, or chromosomal abnormality
- Fetal growth abnormalities
- Maternal-fetal complications that affect the fetus (Rh-sensitization)
Most women have at least one ultrasound during pregnancy. What is its purpose?
To confirm pregnancy and determine EDD
When can fetal genitalia be identified?
by the 12th week
What type of ultrasounds are given during the first trimester?
Transvaginal
What is the purpose of the first trimester ultrasounds?
- Confirm preg, number of fetuses, gestational age
- Determine implantation location and location of maternal anatomy
- ID’s markers such as nuchal transluscency
What is the purpose of second trimester ultrasounds?
- Confirm fetal viability
- Evaluate fetal anatomy, including umbilical cord, vessels, and insertion site
- Determine gestational age
- Assess serial fetal growth
- Evaluate quantity of fluid
- Compare fetal growth and AF in multifetal gestations
- Evaluate four or five markers in a biophysical profile
- Locate the placenta when previa is suspected
- Determine fetal presentation
Why is gestational age determination less accurate after the first trimester?
because the combination of individual growth potential and intrauterine environment causes greater variations among fetuses
What is included in first trimester screening?
- Nuchal Translucency
- Maternal serum plasma protein –A and hCG
An enlarged nuchal translucency is defined as____
-What are the implications of this?
- 3mm or greater or above the 99th percentile
- Asscoiated with tristomy 21 and structural abnormalities like heart defects
hCG level in maternal blood normally ___ every ___ days for the first ___ weeks of pregnancy
-When does hCG peak?
Doubles every 2 days for the first four weeks. Peaks at 8-10 weeks
Increased levels of maternal hCG have been associated with ____ and decreased levels are associated with ____
- Trisomy 21
- Trisomy 13 and 18
What is plasma protein-a (PAPP-A)? Decreased levels in the first trimester are linked to ___
- Glycoprotein made by the placenta and is released directly into the maternal bloodstream
- Trisomy 21
What are some independent first trimester ultrasound markers
- Nasal bone assessment (11-14 weeks)
- Hypoplasia and flat nose
What is Cell-free fetal DNA (cfDNA)?
Small fragments of cfDNA originating from maternal and fetal cell breakdown at the placental level mix freely in maternal circulation
cfDNA screening is used to screen for ___
- Trisomy 21, 18, 13
- Sex chromosome somposition
- Microdeletions and microduplications
What makes cfDNA analysis challenging?
the test can’t distinguish between fetal and maternal DNA leading to false results
can neural tube defects be ID’ed with cfDNA?
No
What is the function of the second trimester multiple marker screening?
Reports a woman’s risk for trisomy 21, 18 and NTD
When is the optimal time to do the second trimester multiple marker screening? What is the full range of this screening?
between 16-18 weeks
-full range is 15-22 6/7
What is included in the second trimester multimarker screening? What is the common characteristic of these hormones/proteins?
-hCG
-Alpha-fetoprotein
-Inhibin A
-Unconjugated estriol (uE3)
These hormones and proteins are produced by the fetus or the placenta and cross over into maternal circulation
What does the triple screen measure?
hCG, AFP, uE3
How is risk calculated in second trimester multimarker screenings?
Computer risk calculations use serum values along with demographic information to calculate risks
What is AFP?
Glycoprotein that is produced early in the first trimester in the yolk sac and eventually from the fetal GI system
Where is AFP produced?
Fetal plasma, then into urine, swallowed and digested
Where can AFP be found?
- AF
- Fetal circulation
- Maternal circulation
AFP levels increase until ___ weeks then they begin to decline
10-14 weeks
Low AFP levels can indicate what three things?
- Trisomies
- Gestational trophoblastic disease
- Normal fetus with an overestimated gestational age or increased maternal weight
Elevated AFP levels are associated with ___
NTD’s
Where is uE3 produced?
Fetal liver and placenta
How levels of uE3 are associated with ___
Trisomy 18, and 21
Inhibin A that is ____ times higher than normal is associated with ___
two
Tri 21
What is an integrated screening?
combines NT measurement and PAPP-A with a quad screen