Genetics Flashcards
an anatomic or structual abnormality which is present at birth
Congenital malformation
Percentage of perinatal deaths that are due to the presence of congenital malformations
20%
Any substance capable of causing abnormal structure in an embryo
Teratogen
Causes of congenital malformations
Genetic factors
Environmental factors
Multifactorial inheritance
Sensitive concept
Certain structures are _________ to certain teratogenic agents at given times and only at given times. _______ event cannot influence the development of a structure if it occurs before or after that structure differentiates or develops
Sensitive,
Noxious
The three catagories that teratogens are devided into are
- Physical agents
- Drugs and chemical agents
- Maternal factors
Radiation,
heat,
mechanical factors like uterine anomalies and fibroids
Physical agents (Teratogen)
DES, Coumadin, alcohol, anti-thyroid drugs, methotrexate, retinoic acid/ vitamin A, valproic acid for seizures, trimethadione, thalidomide, methylmercury, and many others
Drugs and chemical agents (Teratogen)
Include diseases such as diabetes and sickle cell anemia and maternal infections. There are many others
Maternal factors (Teratogen)
Genetic defects that can be identified and diagnosed microscopically
Chromosomal abnormalities
__________________ usually affect a large part of the fetus and Genome are associated with multiple anatomic abnormalities, mental retardation and high mortality rate
Major chromosome abnormalities
Genetic diseases can be the result of:
- An abnormal number of chromosomes such as 13, 18, 21
- Abnormal structure of one or more chromosomes
- Single gene defects which are inherited as autosomal dominant or autosomal recessive
First trimester testing is performed between ______ and _________weeks and involves two parts
11.5 and 13.5
Types of genetic testing done during the firs trimester
- Nuchal translucency
* Maternal blood test of free or total beta hCG and PA PP- A (pregnancy associated plasma protein A)
The combination of the two test done in the first trimester are done to test for
85% of Down syndrome (trisomy 21), & trisomy 18 (Edward’s syndrome)
Measures the fluid filled area at the back of the neck between 11.5 and 13.5 weeks
Nuchal translucency screening
In what plane is the Nuchal translucency screening done?
Sagittal
How is the Nuchal translucency measured?
The measurement is taken inner to inner
Nuchal translucency is normal if it is
less than 3mm
The __________ which is ____________ to the fetus should not be mistaken for increased nuchal translucency
Amnion, adjacent
If the Nuchal translucency is increased,
genetic testing of the fetus is performed
If the fetus has a normal Karyotype
the fetus should be screened for cardiac abnormality in the mid-to-late trimester
PA PP-A and beta hCG are produced by
trophoblastic tissue
Low levels of PA PP-A and beta hCG may indicate
abnormal implantation
poor placentation
risk of trisomy 21
