1. Pregnancy & Newborn Screening Developments
Changes to the Down’s Syndrome
Screening Programme

2. What is screening?
Screening is a public health service in which members of a defined population, who do not necessarily perceive they are at risk of, or are already affected by a disease or its complications, are asked a question or offered a test, to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications
UK National Screening Committee

3. Screening for Down’s syndrome
Screening Tests
Screening tests identify individuals as broadly ‘high’ or ‘low’ chance. High chance results do not indicate that the baby definitely has Down’s syndrome, but should prompt the health care professional to offer further screening or diagnostic tests
Diagnostic Tests
Diagnostic tests for Down’s syndrome give definite information on fetal chromosomes by confirming the presence of a third copy of chromosome 21.

4. Terminology Detection Rate (DR)
The proportion of women who will be identified by the screening test with an affected pregnancy
False Positive Rate (FPR)
The proportion of women with a higher chance/screen positive result but have an unaffected pregnancy
False Negative Rate (FNR)
The proportion of women who are given a lower chance result but have an affected pregnancy
Multiples of the median
The serum marker concentration for a pregnant woman, divided by the median concentration value for unaffected pregnancies of the same gestational age

5. Communicating chance

6. Screening Markers

7. First Trimester Serum Markers
Pregnancy Associated Plasma Protein – A (PAPP – A)
Originates mainly from placental syncytiotrophoblast
Concentration increases with gestation
Screening sensitivity decreases with gestation
Optimal sensitivity at 8 – 9 weeks gestation
Levels reduced in pregnancies affected by Down’s syndrome

8. First Trimester Serum Markers
Free beta Human Chorionic Gonadotrophin (FßhCG)
Beta subunit of hCG/intact hCG
Produced by the syncytiotrophoblast cells
Decreases with gestational age
Sensitivity maintained in second trimester
Raised levels in pregnancies affected by Down’s syndrome

9. Changes to meet new targets and standards
To meet workload standards the four Down’s laboratory services in Scotland are being reconfigured on to two sites:
Glasgow (Yorkhill) serving West of Scotland
Including Highland & Western Isles
Edinburgh (Western General) serving East of Scotland
Including Orkney & Shetland 9

10. First Trimester Screening
Pre-test discussion
Copy of Your Guide to Tests during Pregnancy (48 hrs before test)
Sign consent section of SWHMR (woman & midwife)
Women need to be aware that other conditions may be identified (Edwards, Patau’s)
Combined screening offered for all singleton pregnancies
Multiple pregnancies – NT measurement only 10

11. First Trimester Screening
Remember
Complete ALL sections on form
CHI mandatory (even if hospital no. still in use)
Ideally weight should be at time of test, but if booking weight used MUST be accurate
Record family origin as per Family Origin Questionnaire
If known
record type of assisted conception
Record age of donor if conceived through egg donation
Form must be signed by person taking blood sample
Sonographer MUST record their unique ID code (issued by lab) 11

12. Nuchal Translucency Measured between 11 – 13 weeks 6 days
CRL mm
Must be as accurate as possible
Take more than one image and record the maximum one that meets all criteria
If not possible to obtain NT measurement offer return appointment within 3 working days (provided still in gestational range)
If unable to obtain measurement at repeat – offer second trimester screening 12

13. First Trimester Screening
NT measurement combined with results of serum markers
Results are converted to MoM and corrected for co-variables including maternal weight, smoking status, and if applicable, previous affected pregnancy
NT measurement and blood test performed on same day
Detection rate – 90%
False positive rate – 5%
This test does not screen for neural tube defects and the 18 – 21 week fetal anomaly scan is now the screening test of choice for these conditions

14. Second Trimester Serum Screening
Women who book too late for 1st trimester screening will be offered the quadruple test in the second trimester
15 weeks + 0 days – 20 weeks + 6 days
Alpha-fetoprotein (AFP)
Human Chorionic Gonadotrophin (Intact hCG)
Unconjugated estriol (uE3)
Inhibin-A
Detection rate – 75%
NB. Abnormal AFP results will continue to be reported

15. Second Trimester Serum Screening
Remember
Use specific form for second trimester screening
Complete ALL sections on the form
Clotted samples are required
DO NOT use bottles containing EDTA 15

16. Clinical follow up
If the screening test result indicates the woman is in the “higher chance” group she will be offered counselling and a diagnostic test
Amniocentesis – performed between 15 – 20 weeks
Chorionic villus sampling (CVS) – performed between 11 – 13 weeks
Both of these diagnostic procedures carry a risk of miscarriage, quoted as 2% for CVS and 1% for amniocentesis by most hospitals.

17. Information
Information needs to be given in a way that helps make it clear to the parents that the health professional recognises the impact the diagnosis will have on the parents
The diagnosis of abnormalities which are perceived by health professionals as ‘less severe’ than others still cause significant distress for parents
(Statham, Solomou & Green, 2003)
For parents, the quality of the care they receive is crucial. Few forget their experience of loss. Most have vivid memories of what happened, what was done and what was said and these memories may stay with them for months, years and often a lifetime to come
For further information go to:

18. Useful Web Sites www.pnsd.scot.nhs.uk www.screening.nhs.uk/