Antenatal Screening Flashcards
What antenatal screening is offered in Wales?
- Early pregnancy USS
- Fetal Anomaly USS
- Blood groups + Antibodies
- Hepatitis B
- HIV
- Sickle Cell + Thalassaemia
- Down’s syndrome screening
What is the purpose of the early pregnancy scan?
- Determine viability of pregnancy
- Estimate gestational age
- Take measurements required for Down’s syndrome screening programme
- Detect multiple pregnancies
- Detect some major fatal abnormalities ( large NTD)
How is the gestational age calculated?
Age from last menstrual period - count 2 weeks before conception occurs as pregnant
What measurements are taken in the early pregnancy scan?
Ultrasound used to measure
- Crown-rump length - more accurate earlier its done
- Head circumference if crown-rump length above 84mm
What is the purpose of the Nuchal translucency scan?
- NT = measurement of depth of translucency at back of fetal neck using US
N.B. Difficult to do in obese women
What is the Fetal anomaly scan?
- Look for structural abnormalities in fetus
- Offer support + advice if identified
- Where lethal -> discuss management options (inc. termination if appropriate)
When is the Fetal anomaly scan done?
18 weeks - 20 weeks + 6 days
When is the NT scan done?
11 weeks - 13 weeks + 6 days
What are open neural tube defects, what causes them and how are they diagnosed?
- Includes Spina bifida, Acrania + Anencephaly
- Causes by reduced folic acid
- Lab findings = elevated AFP detectable at quad test
What is screened for in bloods during pregnancy?
- Syphilis
- Hepatitis B
- HIV
- Rhesus antibodies
- Down’s syndrome
- Sickle cell + thalassaemia
- FBC + blood group - anaemia
How is Down syndrome diagnosed?
- Risk increases with maternal age (40+ or 18-)
- US findings = increased NT
- Lab findings =
- Elevated hCG + INH-A
- Lower than average levels of MSFAP + unconjugated Oestriol
What is the rationale for Down syndrome screening?
- Not diagnostic - high/low risk result
- High risk pregnancies offered diagnostic test
- +ve result offered termination of pregnancy
- Screening via combined or quadruple test
Compare the quadruple and combined screening tests for Down’s syndrome
- Combined done earlier
- Combined has better detection rate
- Quadruple used for obese women
What are the 2 types of diagnostic screening offered?
- Chorionic villus sampling (CVS)
2. Amniocentesis
How does CVS work?
- Chorionic villi aspirated through abdomen under US guidance
- Sample sent to genetic lab immediately
- Results within 3 WD’s + full karyotype within 14 WD’s
