Antenatal Screening

Question 1

What is involved in pre-pregnancy counselling?

Answer 1

Optimise maternal health
Smoking cessation
Folic acid: 400mcg
Vitamin D 10mcg daily
Stop/change unsuitable drugs
Advise regarding complications associated with maternal medical problems
Risk of recurrence of Caesarean section, DVT, pre-eclampsia
Risk of recurrence of pre-term delivery, intrauterine restriction, fetal abnormality.

Question 2

What is the standard dose of folic acid given to pregnant women?

Answer 2

400mcg daily

Question 3

What is involved in an antenatal examination?

Answer 3

Routine enquiry
Blood pressure (detect evolving hypertension)
Urinalysis 
Abdominal palpation 
Determine fetal presentation 
Listen to fetal heart

Question 4

What can be assessed during an palpation of the pregnant abdomen?

Answer 4

Symphyseal fundal height
Estimate size of baby
Estimate liquor volume

Question 5

What infections are screened for in pregnancy?

Answer 5

Hep B
Syphilis
HIV
UTI

Question 6

When is anaemia screened for?

Answer 6

12 and 28 weeks

Question 7

What is identified during the first visit ultrasound scan?

Answer 7

Ensure pregnancy viable
Multiple pregnancy?
Identify abnormalities incompatible with life
Offer and carry out Down’s syndrome screening

Question 8

What is identified in a detailed anomaly scan?

Answer 8

Systematic structural review of baby
Not possible to identify all problems
Can identify problems that need intrauterine or postnatal treatment

Question 9

When is first trimester screening carried out?

Answer 9

10-14 weeks gestation

Question 10

What is measured in the first trimester screening ?

Answer 10

Maternal risk factors
Serum B-hCG
Pregnancy associated plasma protein A (PAPP-A)
Fetal nuchal translucency (NT) measurement

Question 11

What is nuchal translucency used to detect?

Answer 11

Screening by NT can detect about 80% of fetuses with trisomy 21

The combination of NT and maternal serum free β-hCG and PAPP-A improves the detection to 90%.

Question 12

What happens with a high risk result in first trimester screening?

Answer 12

Further testing is offered if risk of Down’s syndrome is >1 in 150
Options: • CVS • Amniocentesis • Non-invasive Prenatal testing

Question 13

What is non-invasive prenatal testing?

Answer 13

Maternal blood taken
● Can detect fetal cell free DNA released from the placenta
● No risk of miscarriage
● Not diagnostic, so if gives a high risk result, parents are offered CVS/amniocentesis

Question 14

When is Chorionic venous sampling carried out if requested?

Answer 14

Between 10-14 weeks

Question 15

What is the risk of miscarriage with CVS?

Answer 15

1-2% risk of miscarriage

Question 16

When is amniocentesis carried out if requested?

Answer 16

15 weeks and onwards

Question 17

What is the risk of miscarriage with amniocentesis?

Answer 17

1%

Question 18

What tests and when are used to screen for neural tube defects?

Answer 18

First trimester ultrasound to detect anencephaly and sometimes spina bifida (variants of NTD)

Second trimester biochemical screening
Carried out if not able to get NT measurement Maternal serum is tested for alpha fetoprotein >2.0MoM is high risk and warrants investigation

Second trimester (20wk) ultrasound will detect >90% of NTD

Question 19

What is the purpose of second trimester US?

Answer 19

Second Trimester ultrasound is performed with the purpose of detecting fetal abnormality
This is a good screening test for major structural abnormalities but a poor test for chromosomal abnormalities

Question 20

What percentage of fetuses with T21 will have a normal US scan?

Answer 20

50%