Prenatal screening

Question 1

Commonest cause of term stillbirth (5)

Answer 1

Preeclampsia
Abruption
Unexplained
Infection including GBS
Congenital abnormality

Question 2

Common fetal anomalies

Answer 2

Hypospadias
Down syndrome
Neural tube
Hernia

Question 3

Detection of anomalies dependant on

Answer 3

Primary or tertiary service
Type of anomaly- higher for NTD vs CHD
Gestation
High or low risk

Question 4

Maternal age and risk of down syndrome at birth, age 20, 30, 35, 40, 44

Answer 4

1 in 1500
1 in 900
1 in 360
1 in 100
1 in 50

Question 5

Which aneuploidy has same risk regardless of age

Answer 5

Triploidy

Question 6

Current down syndrome screening- Combined first trimester screen

Answer 6

Maternal age
Fetal nuchal translucency
Nasal bone
Maternal serum bHCG
PAPP-A at 11 - 13 +6

Question 7

When is the CFTS done

Answer 7

11-13 +6 weeks

Question 8

If CFTS cannot be done, what is an alternative

Answer 8

Second trimester biochemistry at 15-20 weeks

Question 9

Is the morphology scan at 20 weeks a screening test for aneuploidy

Answer 9

No

Question 10

What is the false positive rate for prenatal screening for Downs

Answer 10

5%

Question 11

When is amniocentesis performed

Answer 11

15-18 weeks

Question 12

When is chorionic villous sampling performed

Answer 12

10-12 weeks

Question 13

Steps to calculate trisomy 21 risk

Answer 13

Step 1: Maternal age
Step 2: Background aneuploidy risk, increases with previous aneuploidy
Step 3: NT
Step 4: gestation
Step 5: free bHCG and PAPP-A

Question 14

When does NT increase normally

Answer 14

With increasing CRL

Question 15

Does NT increase with increasing T21 risk or reduce

Answer 15

Increases

Question 16

How does risk of T21 change with increasing gestation

Answer 16

Decreases with increasing gestation

Question 17

If lost/has baby with aneuploidy, recommendations for next pregnancy

Answer 17

Some delay before trying 6-12 months
Screening test - risk now increased
Definitive testing
CVS at 12 weeks

Question 18

Fetal loss rate with CVS

Answer 18

1-2%

Question 19

How long do results take with CVS

Answer 19

2 weeks

Question 20

Advantage and disadvantage of CVS

Answer 20

Quicker, can do suction currette if aneuploidy

1-2% fetal loss

Question 21

How long for amnio results

Answer 21

3 weeks

Question 22

Major disadvantage to amniocentesis

Answer 22

If termination- requires induction

Question 23

Management of abnormal results in AC or CVS

Answer 23

Wait and see

Termination

Question 24

Termination of pregnancy

Answer 24

suction, GA, prostaglandin 8-10 hours prior (Misoprostol)

16-20 weeks->induce with PG

Question 25

What is cell free fetal DNA (MPS)

Answer 25

Detectable from 7 weeks | Fetal DNA in maternal plasma derived from placenta via apoptosis

Question 26

What does massive parallel sequencing do

Answer 26

Counts the relative proportion of DNA fragments from different chromosomes, therefore if trisomic the relative amount of DNA from that chromosome will be more

Question 27

What does NIPT test for

Answer 27

T21, T13, T18 45X

Question 28

Compare NIPT to Amniocentesis

Answer 28

Does not pick up all xsome abnormalities | Still requires definitive testing if abnormal result

Question 29

What is the routine second trimester test and what is the timing

Answer 29

Morphology scan | 18-20 weeks

Question 30

Limitations of morphology scan

Answer 30

Maternal obesity Abdominal/pelvic scars Fetal lie, crowding, oligo/anhydramnios, polyhydramnios

Question 31

Survey scan

Answer 31

``` Pelvic, uterine masses Fetal number Fetal viability Fetal lie Amniotic fluid ```

Question 32

What should be documented with regards to the placenta

Answer 32

``` Position Relation to the os Ant/post/lateral Clear of os, low lying, placenta previa Report distance from lower edge of placenta to internal os Myometrium behind placenta Cord insertion into placenta ```

Question 33

What are the biometric measurements (5 + others)

Answer 33

``` Biparietal Head circumference Adbominal circumference Femur length Humerus length Lateral ventricles, CM, NF, nasal bone, cervical length ```

Question 34

Rules of thumb for biometric measurements

Answer 34

Measure the BPD, FL and HL twice, if not within 2 mm, measure a third time Measure the HC and AC twice, if not within 5mm, measure a third time

Question 35

Anatomic assessment of head and neck

Answer 35

``` Skull Cerebellum Cisterna magnum Lateral ventricles Falx Cavum septu pellucidi Cerebral hemispheres ```

Question 36

Anatomic assessment of face

Answer 36

Profile nasal bone Orbits Nose/lips

Question 37

Anatomic assessment of chest

Answer 37

4 chamber heart view with outflow tracts | Lungs

Question 38

Anatomic assessment abdomen

Answer 38

``` Stomach Kidneys Bladder Liver Diaphragm Abdo wall/cord insertion 3 vessel cord ```

Question 39

Other first trimester US markers

Answer 39

``` Nasal bone FHR TR Ductus venosous Frontomaxillary facial ```

Question 40

Purpose of markers

Answer 40

Reduce the false positiv rate but maintain the sensitivity

Question 41

When are the other markers useful

Answer 41

In the intermediate group 1 in 50 to 1 in 1000 for T21

Question 42

What is US fetal tachyC and what is it a marker for

Answer 42

>175 Trisomy 13 improves detection by 5%

Question 43

How does FHR help distinguish T13 and 18

Answer 43

T13 faster, T18 slower

Question 44

What is TR a marker for

Answer 44

T21

Question 45

What percent of T21 have normal morphology scan

Answer 45

50%

Question 46

Soft markers on morphology scan for Downs

Answer 46

``` Pyelectasis >4mm Hypoplasia of 5th metacarpal Absent or hypoplastic nasal bone Hyperechoic bowel Nuchal fold >6mm Echogenic cardiac focus ```

Question 47

Isolated soft marker not requiring further scan and why

Answer 47

Echogenic intracardiac focus Choroid plexus cysts Cystic space >5mm in choroid 1-3% in normal population

Question 48

Isolated soft markers to follow up

Answer 48

``` Multiple Thickened NF Hypoplastic NB AP renal pelvis >4mm Echogenic bowel > bone Mid trimester short long bones ```

Question 49

Second trimester anomalies requiring tertiary

Answer 49

``` Ventriculomegaly Cardiac Omphalocele Gastroschisis Renal tract abnormal NTD ```

Question 50

Risks of amniocentesis

Answer 50

``` Pain, cramping Vaginal spotting Amniotic fluid leakage Amnionitis 1 in 200 fetal loss ```

Question 51

Complications of CVS

Answer 51

Preterm PROM Fetal injury