antenatal testing Flashcards
screening timeline
What does T13, T18 and T21 using ultrasound test do?
Tells you if a baby is growing normally
screening timeline
when is the glucose tolerance test done
done in first 4 weeks of pregnancy
screening timeline
Overview the tests carried out in the antenatal phase of pregnancy
Initially:
- blood tests for sickle cell and thalassaemia
- later blood tests for T21, T18, T13
vaccinations
What are the 5 infections that Pregnant women need to be vaccinated against (TORCHes)
think TORCHes
- Toxoplasmosis
- Others (syphilis, hep B)
- Rubella
- Cytomegalovirus (CMV)
- Herpes Simplex/HIV
downs syndrome
What is down’s syndrome
Congenital disorder due to trisomy (extra copy) of chromosome 21
downs syndrome
Why is screening needed for the large, low risk population
90% of pregnancies occur in women under 35
testing for downs syndrome
Why is amniocentesis not suitable for mass screening and what is used instead
for first part think risk and time
- Amniocentesis is too risky and time consuming for mass screening
- Combined test is used instead
testing for downs syndrome
What is the combined test
think 2 types of markers and age
Combination of ultrasound markers and biochemical markers with maternal age.
testing for downs syndrome
what are the biochemical and ultrasound markers used in the combined test
think type of serum levels and plasma protein-A and BhCG for biochemical
for ultrasound think a type of translucency
Biochemical markers:
- maternal serum levels of pregnancy associated with plasma protein-A (PAPP-A) serum and free BhCG
Ultrasound markers:
- nuchal translucency
diagnostic tests
What are diagnostic tests for downs and turners syndrome
- Amniocentesis
- Chrionic Villus sampling (CVS)
diagnostic tests - amnio vs CVS
What is amniocentesis, in what weeks of pregnancy can it be done, how accurate is it in detecting major autosomal trisomies, how are results received and how long does it take and what are these trisomies
- Fluid removed by ultrasound guided needle inserted into uterus
- can be done between weeks 12-34
- 90-100% accurate
- results by qPCR within 24h
Trisomies:
- trisomy 21: Down’s
- trisomy 18: Edwards
- Trisomy 13: Patau
diagnostic tests - amnio vs CVS
what is chorionic villus sampling, what weeks of pregnancy can it be done and when are results received
- chorionic villi sample is removed from developing placenta
- can be done in weeks 11-14
- results received in 3 days
antenatal screening
Why is antenatal screening in the 1st trimester an advantage?
think:
- timing of information
- invasive procedures
- detection of things
- dating pregnancy
- Information earlier so more options for parents
- Reduced number of invasive procedures
- May detect other anomalies/risk of anomaly at time of scan
- Can date pregnancy accurately
haemolytic disease of the Newborn
What is a Haemolytic Disease of the Newborn
for step 1, think red blood cells being attacked
for step 2, think why antibodies are produced
for step 3, think what is administered if rh blood group is rh negative
- Red blood cells of the fetus/newborn are attacked by maternally derived antibodies
- Maternal antibodies produced as a direct result of a blood group incompatibility between mother and fetus with ans directed against the Rhesus (Rh) antigen on fetal erythrocytes
- If blood group is Rh negative, an injection of anti-D immunoglobulin is administered to prevent you from developing antibodies against your baby’s blood cells in future pregnancies
