Ch 53 Powerpoints Flashcards
Chromosomes
Each cells holds genes
An error in number or structure of the chromosomes causes an abnormality
Normal cell has 46 chromosomes of two pairs of 23
Aneuploid
A cell that has an abnormal number of whole chromosomes
There may to too may or too few
Diploid
A cell having the normal pair of each chromosome. Normal cells are diploid, with the exception of the gametes
Haploid
A cell having only one member of each pair of chromosomes
Monosomy
A cell having only one of an individual chromosome
Mosaic
A situation in which some cells have an abnormal number of chromosomes, while others do not
Triploid
A cell having 3 times the normal haploid number
Trisomy
A cell having three copies of an individual chromosome
Anomalies
A structural feature that differs from the norm
EX: agenesis of the corpus callosum in which there is a congenital abscense of an important midline brain structure
Syndrome
A group of clinically observable findings that exist together and allow for classification
These signs and symptoms are linked to each other in some way
Chromosomal abnormalities often exist when there are multiple defects
Ex: Down Syndrome has clinically identifiable signs such as flat facial profile and a transverse crease in the palm of the hand
Malformation
A structural abnormality that results from unusual development
EX: Dandy-Walker malformation a congenital brain malformation that is thought to be caused by a developmental deviation in the roof of the fourth ventricle
Triple screen
A maternal blood test in the second trimester for detection unusual levels of certain proteins or hormones with chromosomal
Triple test has a 60% chance of detecting Down syndrome
abnormalities
Triple screen- Three lab Values
AFP, estriol, and hCG
AFP- produced in the yolk sac and fetal liver
Estriol and hCG are produced by the placenta
Quadruple screen
The triple screen plus two proteins can be monitored which are produced by the placenta
PAPP-A: pregnancy associated plasma protein A
Dimeric inhibin A
Fetal Karyotyping and Genetic Testing
Advanced maternal age is considered to be 35 years of age or older
Patients with advanced maternal age have a greater risk of having an abnormal pregnancy of pregnancy failure
Fetal karyotyping is an analysis of fetal chromosomes and frequently recommended
Three main procedures for obtaining material for fetal karyotyping
chorionic villi sampling, amniocentesis, cordocentesis
Transvaginal chorionic villi sampling
Earliest procedure
Small amount of chorionic villi is obtained for chromosomal testing
Performed TA or TV 10-12 gestational weeks
Transabdominal chorionic villi sampling
Under ultrasound guidance, a needle or plastic catheter is placed into the placental mass for the aspiration of trophoblastic cells
Fetal loss rate is approx 0.8%
Amniocentesis
Used for genetic purposes at around 15 weeks
Performed transabdominally with ultrasound guidance
Physician inserts a 20 to 22 gauge needle through the abdomen and into the anmiotic sac to remove amniotic fluid
The most common side effects are uterine contractions and cramping
Rarely patients experience vaginal spotting, amniotic fluid leakage or amnionitis
Fetal loss rate 0.5%
2-3 weeks for complete analysis of the fluid
Cordocentesis
Also referred to as percutaneous umbilical cord sampling (PUBS)
Performed TA at 17 weeks
A needle is placed through the maternal abdomen and into the umbilical cord at its insertion point into the placenta
A sample of fetal blood is removed
Fetal loss rate of 1%
Allows for rapid detection of chromosomal anomalies, requires only 48-72 hours for analysis
