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
An invasive test where a needle is placed within the uterine cavity via the cervix, and samples of the chorion or trophoblastic tissue, cells are obtained to evaluate for chromosomal abnormality
Chorionic villus sampling or CVS
Testing done in the second trimester known as the quadruple is made up of what tests?
- Maternal serum alpha-fetoprotein, MS AFP
- Human chorionic godadotropin, hCG
- Unconjugated estriol or E3
- Inhibin A
a glycoprotein which is produced primarily in the fetal liver. It crosses the placenta into the maternal serum and can easily be detected with a blood test called the maternal serum alpha-fetoprotein
Alphafetoprotein or AFP
When can AFP be evaluated
- Incorrect dates (patient is further along in the pregnancy than she thought) *especially if AFP is decreased
- Multiple gestations
- Open neural tube defects
- Abdominal wall defects
- Sacrococcygeal teratoma in the fetus
- Maternal fetal hemorrhage
- Placental Chorioangioma
Chromosome abnormalities
- Fetal demise
- Trisomy 21/ Down syndrome
- Trisomy 18/ Edwards syndrome
Increased MS AFP
Increased beta hCG
Decrease in E3
Increase in Inhibin A
Trisomy 21/ Down syndrome
Decreased MS AFP
Decreased hCG
Decreased E3
Trisomy 18/ Edwards syndrome
If the ultrasound evaluation fails to establish a cause for abnormal quadruple screen test, then __________ is offered to the patient to evaluate amniotic fluid levels of AFP and for fetal chromosome Karyotyping
Amniocentesis
An invasive procedure whereby ultrasound is used to guide needle placement into the amniotic cavity
Amniocentesis
When is an Amniocentesis performed?
at around 16 weeks
