Obs & Gynae 2 Flashcards
With regards to screening, define ‘detection rate’.
The proportion of individuals who will be identified by screening test.
With regards to screening, define ‘false positive rate’.
The proportion of unaffected individuals with a higher risk/screen positive result.
With regards to screening, define ‘false negative rate’.
The proportion of affected individuals with a low risk / screen negative result.
Name 3 antenatal screening programmes.
- Fetal Anomaly Screening Programme (FASP): Down’s, Edward’s, Patau’s screening
18+0 - 20+ week anomaly scan - Infectious Disease Screening Programme:
Hep B, HIV, Syphilis - Sickle Cell and Thalassaemia Screening Programme
Name 3 Newborn Screening Programmes
- Newborn blood spot screening programme:
CF, Congenital hypothyroidism, Sickle Cell disease, Inherited metabolic diseases (x6) - Newborn hearing programme
- New born + 6-8 week infant physical examination screening programme.
Which chromosomal abnormality is Down’s Syndrome associated with?
Trisomy 21
If a child is diagnosed with Down’s syndrome, which diseases are they at increased risk of developing?
- Childhood Leukaemia
- Epilepsy
- Thyroid disorders
- Alzheimer’s disease
- 40-45% have a heart defect.
Which chromosomal abnormality is Edward’s syndrome associated with?
Trisomy 18
Babies with Edward’s syndrome have an extra copy of Chromosome 18 in each cell.
What is the prognosis for a baby diagnosed with Edward’s Syndrome?
- Most die before they are born, are stillborn, or die shortly after birth
- Babies have a wide range of serious problems:
> heart problems
> unusual head and facial features
> major brain abnormalities
> growth problems
Which chromosomal abnormality is Patau’s syndrome associated with?
Trisomy 13
> Babies with Patau’s syndrome have an extra copy of chromosome 13 in each cell.
What is the prognosis for a baby diagnosed with Patau’s syndrome?
- Most die before they are born, are stillborn, or die shortly after birth
- Associated with multiple severe fetal abnormalities
> 80% have congenital heart defects
> holoprosencephaly
> abdominal wall defects
> urogenital malformations
> abnormalities of hands and feet
Which screening test is used in the first trimester to screen for T21, T18 and T13?
What do the results of this test mean?
Combined test:
- Nuchal translucency measurement (at 11+2 - 14+1 weeks)
- Serum testing: PAPP-A and free b-hCG
Results: Produces two risk results: one for T21 and another for T18/T13.
What is the cut off threshold for offer of diagnostic testing following the combined screening test in the 1st trimester of pregnancy?
Cut off threshold: if the screening test shows that the chance of the baby having Down’s, Edward’s or Patau’s is less than 1 in 150, this is called a ‘Lower Risk’ result.
Which screening tests are offered in the 2nd trimester for T21, T18 and T13?
Quadruple test
- Offered if combined screening not possible: late booker, nuchal translucency not obtained.
- Uses serum markers only: Alpha feto protein, total b-hCG, Estriol and Inhibin A.
- Offered at 14+2 - 20+0 weeks
What factors should you take into account following screening using the quadruple test (2nd trimester of pregnancy)?
- Scan measurements
- Mother’s date of birth
- Serum markers are reported as ‘Multiples of the Median’
- Levels of some markers are affected by ethnicity, smoking, and diabetes
- Mother’s weight is required (as serum levels will reduce with greater blood volume).
What should you do following ‘Screen positive’ results (following pregnancy screening tests)?
- Telephone to screening midwives
- Appointed to fetal medicine unit within 3 days
- Offered diagnostic test: CVS or Amniocentesis
What is the risk of miscarriage following CVS / Amniocentesis?
1 in 100 for a single pregnancy.
1 in 50 for twins.
What alternative is there to CVS / Amniocentesis
- Do nothing
- NIPT (Non-invasive prenatal testing) -> this is NOT available on the NHS. **unless you live in Wales & deemed to be at higher risk **
Describe the principles of non-invasive prenatal testing as a screening tool.
- Only available in the private sector
- Screening test analyses fragments of fetal DNA in maternal blood
- Can be done from 10 weeks of pregnancy
- Predicts the risk of T21, T18 and T13.
- Predicts fetal gender
- Up to 99% detection rate
0. 1% false positive rate.
The fetal anomaly screening (ultrasound) programme offers women a minimum of 2 scans during pregnancy (NICE, 2016).
At what points in her pregnancy is a woman offered these scans? What do the scans screen for?
10 - 14 weeks: Early Ultrasound Scan
> pregnancy dating
> confirm viability
18+0 - 20+6:
> identify structural anomalies
The timing of the scans allows for further diagnostic tests, if required. Ensures women have time to consider decisions about continuing their pregnancy.
The Early USS is conducted at 10 - 14 weeks. What does this screen for?
- Gestational age
- Fetal demise
- Multiple pregnancy
May also reveal: - Fetal abnormality
- Increased nuchal translucency
The mid-pregnancy scan is conducted at 18+0 - 20+6. What is it designed to identify?
- major abnormalities which indicate the baby may die shortly after birth
- conditions that may benefit from treatment before birth
- to plan delivery in an appropriate hospital / centre
- to optimise treatment after the baby is born
- to provide choices for the woman and her family about continuance or termination of the pregnancy.
How are pregnant women screened for infectious diseases?
Blood test (at any stage of pregnancy where the woman presents for care).
Which infectious diseases are screened for in pregnancy?
- HIV: treatment can improve mother’s prognosis and reduce risk of transmission to the baby.
- Hep B: Look for current infection (usually chronic). This will allow for vaccination of the baby and reduce the risk of transmission to baby.
- Syphilis: identify infection. Treatment to prevent congenital syphilis and to prevent complications for the mother.