Ch. 8 Genetic Testing Flashcards
Define teratogen
Any substance capable of causing abnormal structure in an embryo. The term is derived from the Greek word “terato” which means ‘monster’
Causes of congenital malformations include
genetic factors, environmental factors, multifactorial inheritance
What are the three categories of teratogens
Physical agents, drugs and chemical agents, maternal factors
Physical agents of teratogens include
Radiation, heat (hyperthermia between 4-14 weeks ie, saunas and hot tubs)
Signs of fetal alcohol syndrome include
Growth restriction, mental retardation, congenital heart disease, joint anomalies, maxillary hypoplasia
what effects could antithyroid drugs have on a fetus
Polydactyly, goiter
What effects is aspirin (ASA) known or causing on a fetus
Gastroschisis
What is the drug known for causing T-Shaped uterus’ in infants exposed while in utero
DES - Diethylstilbestrol
Single gene defect in which one parent is usually affected by the trait and it is evident in each generation
Autosomal dominant
Single gene defect in which parents are usually unaffected and the trait may appear to skip a generation
Autosomal recessive
A normal, balanced set of chromosomes
Euploid
An unbalanced set of chromosomes
Aneuploidy
The presence of an extra chromosome
Trisomy
The presence of additional set of chromosomes
Triploidy
The genetic makeup of an individual
Genotype
The expression of the genetic makeup of an individual (both physical and physiologic)
Phenotype
During how many weeks is first trimester testing performed
11.5-13.6 weeks
What are the two parts to a first trimester genetic screen
Nuchal translucency scan and a maternal blood test of of total beta hCG and PAPP-A
What types of defects cannot be detected by CVS
Neural tube defects
During what gestational age can an NT be performed, what does the CRL have to measure to be able to evaluate the NT?
11.5-13.6 weeks. the CRL must measure between 45-84 mm.
What trisomies does a thickened NT correlate to
Trisomy 21 (downs) and trisomy 18 (edwards)
What measurement of the NT is considered abnormal
> 3mm
An abnormal NT with a normal karyotype is associated with an increased risk of
Congenital heart disease (CHD)
What does NIPT stand for
Noninvasive Prenatal Testing
At how many weeks can a pt have NIPT
after 10 weeks
Type of genetic sampling that occurs between 9 and 12 weeks, can be performed transcervically or transabdominally with the use of US guidance
Chorionic villus sampling (CVS)
What four levels are sampled in a Quad screen aka a multiple marker
Maternal serum alpha-fetoprotein (MSAFP), hCG, unconjugated estriol, and inhibin A
The markers on a quad screen increase the detection of which defects
Open neural tube defects (ONTD’s).Also trisomy 21 and trisomy 18
Where is AFP primarily produced and when is it considered to be the most accurate?
The fetal liver, between 16-18 weeks. (this is why the quad screen is a second trimester screen)
List causes of an elevated MSAFP
Incorrect dates (30-40% of cases), multiple gestation, ONTD, abdominal wall defects, placenta chorioangioma, maternal fetal hemorrhage, maternal hepatocellular carcinoma.
List reasons of a decreased MSAPF
incorrect dates, chromosome abnormalities, fetal demise
How will each marker in a quad screen be affected in a fetus with trisomy 18 aka Edwards syndrome
MSAFP- Decreased
hCG- decreased
Unconjugated estriol- decreased
How will each marker in a quad screen be affected in a fetus with trisomy 21 aka Down Syndrome
MSAFP- decreased
hCG- increased
unconjugated estriol- decreased
Inhibin A- increased
During what gestation is genetic amniocentesis usually performed
around 16 weeks
What is used in a multiple gestation during genetic amniocentesis in order to ensure the same sac is not being tapped more than once
A dye known as indigo carmine
