Chapter 20: Prenatal Testing and Reproductive Genetics

Question 1

Amniocentesis

Answer 1

Gestational age of performing: 15-16 weeks of gestation
Aspiration of 10-30ml of amniotic fluid from amniotic sac, through abdominal wall under ultrasound guidance
Fetal skin cells are collected by centrifugation and then cultured for two weeks in an incubator
The chromosomes from these fetal skin cells are harvested and reated with hypotonic fixative solution
The fetal cells can be directly used for FISH test
Risk for miscarriages: 0.5-1%

Question 2

Amniotic Fluid

Answer 2

The protective liquid contained by the amniotic sac

Cushion for the fetus

Question 3

Trophoblast

Answer 3

The outer cell mass of the early embryo that gives rise to the placenta

Question 4

Inner Cell Mass

Answer 4

the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus

Question 5

Chorionic Villus

Answer 5

Layer of cells covering a fertilized ovum, some of which will later form the placenta

Question 6

Maternal Cell Contamination

Answer 6

When during sampling, some of the mother’s cells are taken as well as the fetus

Question 7

Chorionic Villus Sampling

Answer 7

the trophoblast layer of the chorionic villus belongs to the fetus, and thus is the targeted tissue in this testing
11 weeks gestation
Risk for miscarriage : 1-2%
Other problem: maternal cell contamination
Transcervical or transabdominal aspiration
Ultrasound used to guide procedure

Question 8

Miscarriage

Answer 8

Also called spontaneous abortion

An event that results in the life of the fetus before 20 weeks

Question 9

Gestation

Answer 9

The process of carrying, or being carried in the womb between conception and birth

Question 10

Maternal decidua

Answer 10

The decidua is the modified mucosal lining of the uterus (that is, modified endometrium) that forms in preparation for pregnancy. It is formed in a process called decidualization under the influence of progesterone. … The decidua forms the maternal part of the placenta and remains for the duration of the pregnancy.

Question 11

Aneuploidy

Answer 11

A chromosome number that is not an exact multiple of the haploid number

Question 12

fluorescent in situ hybridization

Answer 12

Use of a single-stranded DNA sequence with a fluorescent label to hybridize with its complementary target sequence in the chromosomes, allowing it to be visualized under ultraviolet light

Question 13

Ultrasonography

Answer 13

The use of ultrasonic sound waves to image objects at a distance (e.g. the developing fetus in utero)

Question 14

Nuchal translucency

Answer 14

Refers to the assessment of the quality of fluid collecting within the nape of the fetal neck, usually from an ultrasound scan around the end of the first trimester

Question 15

Maternal Serum Screen

Answer 15

Is done around 16 weeks gestation (between 11 and 16)

Neural Tube Defect and Down Syndrome

Question 16

Alpha fetoprotein

Answer 16

the fetal equivalent of albumin and is the major protein in the fetal blood
In NTD it is higher, in Down syndrome, it is lower

Question 17

Folic Acid

Answer 17

The synthetic form of folate which helps to form DNA and other genetic material
Women trying to get pregnant should take up to 400 micrograms folic acid daily until after the first trimester

Question 18

Newborn screen program

Answer 18

In Georgia, each newborn will be tested for some severe diseases
A blood sample will be collected from a baby by pricking its heel
The blood is then put on a piece of paper and air dried
Dry blood is sent to the lab for testing
+ test is sent to another lab to rule out false positive
31 diseases tested in GA including PKU, sickle cell anemia, and CF
critical to be tested within 24-48 hours

Question 19

Non-invasive Prenatal Diagnosis (NIPD)

Answer 19

Cell free DNA screening
Can detect Trisomies 21, 13, 16, 18, 22
Triploidy
Sex chromosome aneuploidy
Achondroplasia (FGFR3 gene mutation)
Some craniosynostosis (FRFR2 mutation)
Not effective if obese, multiples, donor egg, or less than 10 weeks pregnant

Question 20

NTD

Answer 20

Neural Tube Defect
The closure of the spinal cord is abnormal
most severe form is anencephaly
Can be caused by trisomy 13 or 18. Or lack of folic acid
Girls more often
Race: spina bifida is more common among whites and Hispanics