fetal screening

Question 1

at what gestation is the first ‘dating’ scan?

Answer 1

10-13 weeks

Question 2

what is the combined screening test and what does it check?

Answer 2

combined test uses

1. Maternal age
2. Nuchal translucency measurement
3. BHCG
4. PAPP-A
5. gestational the calculated from the crown rump length

The optimal time to preform this is 11=14 weeks

• Beta‑human chorionic gonadotrophin (beta-HCG) – a higher result indicates a greater risk
• Pregnancy‑associated plasma protein‑A (PAPPA) – a lower result indicates a greater risk

Question 3

what are the three trisomy?

Answer 3

Downs= chr 21
Edwards= chr 18 
Pataus= chr 13

Question 4

what is the second trimester quadruple test?

Answer 4

done from 14-20 weeks- for women that book late for the first trimester scanning
it has a lower detection and a higher screen positive rate than the combined test
1. AFP- lower is greater risk
2. HCG- higher is higher risk
3. UE3- lower is higher risk
4. inhibit A- higher is higher risk

Question 5

when does the fetal anomaly scan take place and what does it show?

Answer 5

18- 20 weeks- women can choose if they want the scan. they screen for 11 abnormalities

1. ancephaly
2. open spina bifida
3. cleft lip
4. diaphragmatic hernia
5. gastroschisis
6. exomphalos
7. serious cardiac abnormalities
8. bilateral renal agenesis
9. lethal skeletal dysplasia
10. Edwards syndrome
11. pataus syndrome

Question 6

what are the 2 types of diagnostic testing for trisomy?

Answer 6

1. cvs = preformed from 11 weeks to obtain a sample of the placental tissue for chromosomal analysis. higher chance of miscarrige
2. amniocentesis= happens from 15 weeks onwards and involves taking a sample of amniotic fluid

Question 7

what happens if a low lying placenta is detected at the routine 18-20 week anomaly scan?

Answer 7

• this will usually resolve when the baby is born
• if the placenta is covering the internal cervical os then another scan will be done at 32 weeks to rule out placenta prevue

Question 8

when is anti-D offered to rhesus (-) mothers?

Answer 8

1st dose= 28 weeks

2nd dose= 34 weeks

Question 9

what nuchal thickness may suggest downs syndrome?

Answer 9

> 6mm

Question 10

what is non invasive prenatal testing?

Answer 10

• Uses maternal blood that apparently carries some fetal DNA
• useful to do for mothers with > 1/150 risk of having a downs syndrome baby
  not currently routinely used in the NHS

Question 11

in which case would AFP be raised on a screening test?

Answer 11

neural tube defects

Question 12

in which cases is nuchal translucency increased?

Answer 12

Down’s syndrome
congenital heart defects
abdominal wall defects

Question 13

causes of hyperechogenic bowel?

Answer 13

cystic fibrosis
Down’s syndrome
cytomegalovirus infection

Question 14

which infections are routinely screened for in pregnancy?

Answer 14

Hepatitis B
HIV
Syphilis