Key Area 4- Antenatal and Postnatal Screening

Question 1

What is the purpose of antenatal screening?

Answer 1

.To identify the risk of a disorder so that further tests and a prenatal diagnosis can be offered

Question 2

What is ultrasound imaging?

Answer 2

.When an ultrasound scanner is held against a pregnanat women’s abdomen, it picks up a high-frequency sounds that have bounced off the fetus. These are converted to an ultrasound image on a computer screen. Pregnant women are given two ultra sounds; dating and anomaly.

Question 3

What is a dating scan?

Answer 3

.This ultrasound imaging is carried out at 8-14 weeks to produced a dating scan, which is used to determine the stage of the pregnancy and to calculate the date and when the baby is due to be born
.They are also used with biochemical tests for marker chemicals which vary normally during pregnancy

Question 4

What is an anomaly scan?

Answer 4

.This ultrasound imaging is carried out at 1-20 weeks to produce an anomaly scan, which detects the presence of any serious physical abnormalities in the fetus

Question 5

What are biochemical tests?

Answer 5

.They monitor the concentrations of marker chemicals
.Medical conditions can be detected by a range of marker chemicals that indicate a condition but need not necessarily be directly part of the condition
.They must be used in conjunction with dating scans

Question 6

What is diagnostic testing?

Answer 6

.It is a definitive test that produces results that can be used to establish without a doubt whether or not the fetus is suffering s specific condition or disorder
.They may be offered to women if screening tests have shown a potential problem, there’s a family history of a genetic disorder or she belongs to a high-risk group, such as women over the age of 35

Question 7

What is amniocentesis?

Answer 7

.It is carried out between 14-16 weeks, and involves withdrawing amniotic fluid containing foetals cells.
.The cells are cultures, stained and examined under a microscope to create the karyotype and allows for chromosome abnormalities to be detected
.For example, an extra chromosome 21 indicates down’s syndrome
.Disadvantage= risk of miscarriage, and gives results later in pregnancy
.Advantage= detects neural tube defects

Question 8

What is chorionic villus sampling (CVS)?

Answer 8

.This involves taking a tiny sample of placental cells using a fine tube inserted into the mothers reproductive tract. The cells are cultured and used for karyotyping.
.Disadvantage= causes a higher incidence of miscarriage, and does not detect neural tube defects
.Advantage= it can be carried out at 8 weeks whereas amniocentesis is 14-16 weeks

Question 9

What is a karyotype?

Answer 9

.It shows an individuals chromosomes arranged as homologous pairs
.Cells can be cultured to obtain sufficient cells to produce a karyotype to diagnose a range of conditions