Antenatal Screening Rebecca Sykes

Contents

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 40 + Midwife – membrane sweep each week and discuss IOL at 41 weeks

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

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

Chorionic Villus Sampling Invasive diagnostic test Performed between 11+0 and 13+6 Allows examination of fetal karyotype from placental biopsy Accuracy 97.5% - 99.6% Miscarriage risk – 2% Performed transabdominally usually

Amniocentesis Invasive diagnostic test Performed between 15 weeks and 16 weeks – can be done at any time Accuracy 98-99% Miscarriage risk – 0.5 -1% Allows examination of fetal karyotype Rapid testing (results in 24-48 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 24-48 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)

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  

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 10-14 days Reports as low risk or high risk High risk will be offered CVS or amniocentesis

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