Screening Flashcards
What are the problems with screening tests?
Can give false positives or false negatives, can lead to needless worry.
What is ultrasound imaging used for?
The dating scan at 8-14 weeks and the anomaly scan at 18-20 weeks.
What is the dating scan for?
8- 14 weeks. Estimates the stage of the pregnancy and estimates the due date.
What is the anomaly scan for?
18-20 weeks. Checks for serious physical abnormalities.
How is the due date estimated?
Dating scan and biochemical tests.
What are the different biochemical tests?
Urine test to test for pregnancy. Blood test at 16-18 weeks to test for foetal abnormalities, checks for the three marker chemicals. Regular blood and and blood pressure tests to monitor the health of the mother and baby.
What are diagnostic tests?
Offered if the blood tests show a presence of the three marker chemicals. Aims to determine exactly what is wrong with the baby. Can cause miscarriage.
What is amniocentesis?
A sample of amniotic fluid which contains cells from the foetus is taken and the cells are grown in culture. While the cells divide, their karyotype can be checked for chromosomal abnormalities. 12-14 weeks. 2 weeks for results. 1% chance of miscarriage.
What is CVS?
Chronic Villus Sampling. Sample of placental tissue, cells are grown in culture. Can be done from 8 weeks. 2% chance of miscarriage.
What would a third number 21 chromosome indicate?
Down’s Syndrome.
What is rhesus antibody testing?
Pregnant women have their blood rhesus factor checked as there can be problems if a rhesus negative mother has a second rhesus positive child.
Why is their problems is a rhesus negative women has a second rhesus positive child?
Some of the first baby’s red blood cells will leak across the placenta, as they have rhesus proteins which the mother does not have, the mothers blood will fight off the baby’s red blood cells. Nothing will happen to the first baby but the mother will make antibodies to fight off rhesus positive blood which will travel across the placenta to destroy the baby’s red blood cells if she has a second rhesus positive child.
What can be done to stop rhesus negative mothers’ antibodies attacking her second rhesus positive child’s red blood cells?
Rhesus negative women are given an anti-rhesus injection after their first birth which coats the rhesus positive blood cells and stops the mother from making anti-rhesus antibodies.
What are inborn metabolic errors? Example?
Errors in chemical reactions. PKU.
What causes PKU?
A gene mutation which causes an enzyme to be faulty.
