Endo/Repro - Genetics - Prenatal Diagnosis; Intrauterine Infection; Pregnancy & Teratogens Flashcards
What is α-fetoprotein?
Is it normally found in amniotic fluid?
Fetal albumin;
no
What is a notable situation in which α-fetoprotein leaks into the amniotic fluid?
Are there others?
Neural tube defects;
yes
What is indicated by an increase in α-fetoprotein in a pregnant woman’s serum?
Potential fetal neural tube defect (or other defect)
How much folic acid should a woman be ingesting daily before and after conceiving?
How long before fertilization? How long after?
400 μg;
1 month before — through the first trimester (at least)
At how many menstrual weeks does the neural tube close?
6
A healthy woman presents at clinic indicating that she and her husband are trying to get pregnant. They have one son, who was born with a neural tube defect.
What do you recommend?
What is the risk of large doses of the substance you recommend?
Counseling + larger doses of folic acid (2-4 mg)
masking B12 deficiencies
What are the substances checked in a quad screen?
Maternal serum metabolites:
α-fetoprotein, estriols, β-HCG, inhibin A
When is a quadruple screen useful?
2nd Trimester
Values are predictive at 15-to-20 weeks of gestation
(accurate gestational age is essential)
True/False.
The quad screening is only useful in the third trimester.
False.
The quad screening is meant to be given in the second trimester.
Interpret the following quadruple screen results:
α-fetoprotein — decreased
estriols — decreased
β-HCG — increased
inhibin A — increased
Down syndrome
Interpret the following quadruple screen results:
α-fetoprotein — decreased
estriols — decreased
β-HCG — decreased
inhibin A — unchanged
Trisomy 18 (Edward’s syndrome)
Are all 4 maternal serum metabolites in a quadruple screen necessary for diagnosing neural tube defects?
No;
just α-fetoprotein (increased)
List the expected quadruple screen results for a woman carrying a fetus with Down syndrome (trisomy 21).
α-fetoprotein — decreased
Estriols — decreased
β-HCG — increased
Inhibin A — increased
List the expected quadruple screen results for a woman carrying a fetus with Edward’s syndrome (trisomy 18).
α-fetoprotein — decreased
Estriols — decreased
β-HCG — decreased
Inhibin A — unchanged
List the expected quadruple screen results for a woman carrying a fetus with neural tube defect.
α-fetoprotein — increased
Estriols — n/a
β-HCG — n/a
Inhibin A — n/a
True/False.
A quadruple screen measures fetal serum levels of the following four metabolites:
α-fetoprotein, estriols, β-HCG, inhibin A
False.
A quadruple screen measures maternal serum levels of the following four metabolites:
α-fetoprotein, estriols, β-HCG, inhibin A
Are false positives common in a quadruple screen?
What is the sensitivity for trisomy 21 and trisomy 18?
Not very (~4%);
~75%
(90% for neural tube defects)
List a few techniques via which fetal samples can be obtained for genetic analysis.
Amniocentesis
Chorionic villus sampling
Fetal blood sampling
When can amniocentesis be done for genetic analysis?
Are there any contraindications?
After 15 weeks gestation;
anhydramnios, certain infections
When is chorionic villus sampling performed (if necessary)?
Are there any contraindications?
Between weeks 10 - 13 of gestation;
cervical infections
When can fetal blood sampling be performed?
After 20 weeks
When is it best to perform a fetal ultrasound checking for abnormalities?
Weeks 18 - 20
Combined use of the triple screen and detailed ultrasound detects about __% of Down syndrome.
75
What are some potential indications for a ‘genetic ultrasound’ during pregnancy?
- Advanced maternal age
- Abnormal maternal metabolite screening
- Family history of specific disorder
- Teratogen exposure
(among others)
When is the ‘first screening’ of pregnancy?
What three portions does it entail?
Does it check for neural tube defects?
Mid-to-late 1st trimester;
(1) nuchal translucency measurement, (2) free β-HCG, (3) pregnancy-associated plasma protein;
no (only maternal α-fetoprotein in the 2nd trimester)
If the first screening of pregnancy shows abnormalities, what happens next?
A sequential (integrated) screening in the 2nd trimester;
may include chorionic villus sampling + a quad screen
What is ‘cell free fetal DNA’?
A newer screening test involving analysis of fetal chromosomal fragments in maternal blood
(99% sensitive for trisomy 21 and 18);
done after 10 weeks gestation