Ch 53 PowerPoint Flashcards
Chromosomes
Each cells holds genesAn error in number or structure of the chromosomes causes an abnormalityNormal cell has 46 chromosomes of two pairs of 23
Aneuploid
A cell that has an abnormal number of whole chromosomesThere 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 normEX: 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 classificationThese signs and symptoms are linked to each other in some wayChromosomal abnormalities often exist when there are multiple defectsEx: 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 developmentEX: 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 syndromeabnormalities
Triple screen- Three lab Values
AFP, estriol, and hCGAFP- produced in the yolk sac and fetal liverEstriol and hCG are produced by the placenta
Quadruple screen
The triple screen plus two proteins can be monitored which are produced by the placentaPAPP-A: pregnancy associated plasma protein ADimeric inhibin A
Fetal Karyotyping and Genetic Testing
Advanced maternal age is considered to be 35 years of age or olderPatients with advanced maternal age have a greater risk of having an abnormal pregnancy of pregnancy failureFetal 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 cellsFetal loss rate is approx 0.8%
Amniocentesis
Used for genetic purposes at around 15 weeksPerformed transabdominally with ultrasound guidancePhysician 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 crampingRarely patients experience vaginal spotting, amniotic fluid leakage or amnionitisFetal 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 weeksA needle is placed through the maternal abdomen and into the umbilical cord at its insertion point into the placentaA sample of fetal blood is removedFetal loss rate of 1% Allows for rapid detection of chromosomal anomalies, requires only 48-72 hours for analysis
Down Syndrome (Trisomy 21)
Most common chromosomal abnormality
Occurs in 1 in 500 to 800 pregnancies
Fetuses have an extra chromosome 21
Down Syndrome (Trisomy 21)- Maternal Serum Screening
Low AFP Low Estriol High hCG High inhibin A Low PAPP-A
Down Syndrome (Trisomy 21)- Sonographic Findings
Absent nasal bones (hypoplastic nose) Brachycephaly Clinodactyly Duodenal atresia Echogenic intracardiac focus Hyperechoic bowel Macroglossia Mild hydrocephalus Nuchal thickening >/= 6mm between 16 and 20 weeks Thickened nuchal translucency Pericardial effusion Pyelectasis Sandal gap Shortened limb VSD’s Widened pelvic angles
Edwards Syndrome (Trisomy 18)
Majority of fetuses die either before birth or shortly after birth
Fetuses have an extra 18 chromosome
All laboratory values are decreased
Edwards Syndrome (Trisomy 18)- Maternal Serum Screening
Low AFP Low estriol Low hCG Low inhibin A Low PAPP-A
Edwards Syndrome (Trisomy 18)- Sonographic Findings
Strawberry shaped skull Agenesis of the corpus callosum Choroid plexus cyst Hypoplastic cerebellum Enlarged cisterna magna Micrognathia Small, low-set ears Esophageal atresia Spina bifida Clenched hands, overlapping index finger, fixed wrists Cardiac defects Omphalocele Diaphragmatic hernia Renal anomalies Single umbilical artery Feet abnormalities
Patau Syndrome (Trisomy 13)
Holoprosencephaly and abnormal facies are common findings with Patau syndrome
Fetuses have an extra chromosome 13
Almost always a fatal condition, fetus typically dies in the neonatal period
Maternal serum screening not always beneficial in the diagnosis of this condition
Patau Syndrome (Trisomy 13)- Maternal Serum Screening
Not always beneficial
Possible low AFP
Possible low inhibin A
Patau Syndrome (Trisomy 13)- Sonographic Findings
Microcephaly Polydactyly Holoprosencephaly Ventriculomegaly Agenesis of the corpus callosum Small, low set ears Facial anomalies(cyclopia, cleft lip, cleft palate) Cardiac defects Omphalocele Renal anomalies Single umbilical artery Clubfeet
Triploidy
Chromosomal abnormality in which the fetus has 69 chromosomes instead of the normal 46
Three sets of 23
Fetuses die in first or second trimester
Two types of triploidy, Type I and Type II
Often a partial molar pregnancy is found with a triploid fetus
Elevated hCG, bilateral ovarian theca lutein cysts
Triploidy - 1st Trimester Sonographic Findings
Cystic spaces seen within an enlarged placenta(molar pregnancy)
Fetal demise
Bilateral ovarian theca lutein cysts
Triploidy -2nd and 3rd trimester Sonographic Findings
Holoprosencephaly Dandy-Walker malformation Agenesis of the corpus callosum Hydrocephalus Facial abnormalites (microphtalmia and micrognathia Small, low set ears Cardiac defects Renal anomalies IUGR Omphalocele Single umbilical artery Syndactyly (third and fourth fingers Clubfeet
Turner Syndrome
Disorder typically found in females
May also be referred to as monosomy X, as most often the paternal sex chromosome is missing
Classically presents with a nuchal cystic hygroma and nonimmune hydrops
Nonimmune hydrops is a buildup of fluid within at least two body cavities
Often fatal condition, spontaneous AB in first or second trimester
Turner Syndrome- Maternal Serum Screening
Low AFP Low hCG (with hydrops) Low estriol Low inhibin A(with hydrops) Low PAPP-A
Turner Syndrome- Sonographic Findings
Increased nuchal transluceny
Cystic hygroma
Renal anomalies (horseshoe kidneys and renal agenesis
Cardiac defects (coarctation of the aorta)
Nonimmune hydrops (ascites, pleural effusion, pericardial effusion, subcutaneous edema)
