1. Antenatal Screening
Rebecca Sykes

2. Contents

3. Pregnancy schedule Week 8 to 12 Midwife – Booking appointment - bloods
Week 12 to 14 Dating Scan
Week 16 Midwife – results of screening
Week 18 to 20 Anomaly Scan
Week 25 Midwife
Week 28 Midwife – Anti-D, Bloods
Week 31 Midwife – only if first pregnancy
Week 34 Midwife – Discuss birth plan, 2nd Anti-D
Week 36 Midwife – Check position of baby, consider ECV
Week 38 Midwife
Week Midwife – membrane sweep each week and discuss IOL at 41 weeks

4. Screening Bloods Thalassaemia – All women
Sickle cell disease – High risk women (family origins and geographical areas)
HIV
Hepatitis B
Syphilis
Rubella
Sickle cell disease mainly affects people of African, Caribbean, Middle Eastern, Eastern Mediterranean and Asian origin. 
In the UK, it's particularly common in people with an African or Caribbean family background.
IF mum found to be a carrier – dad is screened

5. Screening for Down’s, Edward’s and Patau’s
10-14 weeks – Combine Test
Bloods – PAPP-A (pregnancy associated plasma protein-A) and free B-hCG
Ultrasound – Nuchal translucency
14 – 20 weeks – quadruple test
Bloods – Free B-hCG, alpha fetoprotein, inhibin-A and unconjugated estriol
Both give high or low risk
Anything more than 1:150 – Offer diagnostic testing

6. Chorionic Villus Sampling
Invasive diagnostic test
Performed between 11+0 and 13+6
Allows examination of fetal karyotype from placental biopsy
Accuracy 97.5% %
Miscarriage risk – 2%
Performed transabdominally usually

7. Amniocentesis Invasive diagnostic test
Performed between 15 weeks and 16 weeks – can be done at any time
Accuracy 98-99%
Miscarriage risk – %
Allows examination of fetal karyotype
Rapid testing (results in hours).
Down's syndrome (trisomy 21).
Edward's syndrome (trisomy 18).
Patau's syndrome (trisomy 13).
Turner syndrome.
Klinefelter's syndrome.
Other sex chromosome anomalies.
Performed transabdominally usually
On the amniotic fluid:
AFP and acetylcholinesterase levels (for neural tube defects).
Bilirubin levels (for gestational assessment and to detect isoimmune haemolysis).
Tests of lung maturity (various - for example, lecithin-to-sphingomyelin ratio).
Enzyme analysis (many and varied, including for inborn errors of metabolism).
On fetal cells extracted from amniotic fluid testing for genetic and chromosomal disorders:
Rapid testing (results in hours)[4]. In most areas this will identify specifically:
Down's syndrome (trisomy 21).
Edward's syndrome (trisomy 18).
Patau's syndrome (trisomy 13).
Turner syndrome.
Klinefelter's syndrome.
Other sex chromosome anomalies.
Chromosome analysis after cell culture (results take about two weeks). This will give full karyotyping but even this will not identify all chromosomal abnormalities.
Other possible tests on fetal cells (appropriate genetic counselling may preclude the need):
Direct DNA analysis techniques (for example, for Tay-Sachs disease, phenylketonuria, Duchenne muscular dystrophy and cystic fibrosis).
Indirect DNA analysis (used, for example, to detect linkage disorders when the exact gene is not known)

8. Anomaly scan
Look at fetal bones, heart, brain, spinal cord, face, kidneys and abdomen.
Anencephaly
open spina bifida
cleft lip  
diaphragmatic hernia 
gastrochisis 
exomphalos 
serious cardiac abnormalities 
bilateral renal agenesis
lethal skeletal dysplasia 
Edwards' syndrome, or T18 
Patau's syndrome, or T13  

9. Non-Invasive Prenatal screening
Can be done around 10 weeks
Taking a maternal blood sample +/- USS
Costs between £350-£550
Down’s, Edward’s and Patau syndrome – very accurate
Other clinics look for micro-deletions – unsure how accurate this is or useful
Results take days
Reports as low risk or high risk
High risk will be offered CVS or amniocentesis

10. Any Questions?