Antenatal Screening

Question 1

What is difference between diagnostic and screening test?

Answer 1

Screening - no symptoms, evaluate individual’s risk of developing a disease whereas diagnostic - symptoms often, identifies presence of specific disease

Question 2

How do we assess the robustness of a screening test?

Answer 2

Sensitivity and specificity

Question 3

What blood tests are carried out at booking visit? (6)

Answer 3

Hb, 
ABO; Rhesus status and antibodies, 
syphillis; 
HIV; 
Hep B + C, 
urinalysis

Question 4

What is the purpose of the ultrasound performed at booking scan? (5)

Answer 4

Confirm viability, 
singleton/multiple pregnancy chorionicity, 
estimate gestational age & EDD, 
detect major structural abnormalities, 
offer trisomy screening

Question 5

What is Naegele’s Rule?

Answer 5

Predicts an estimated due date based on the onset of woman’s last menstrual period. Add on nine months and seven days (280 days)

Question 6

What are 3 possible reasons for an empty gestational sac in uterus in ultrasound?

Answer 6

anembyronic thus non-viable,
OR very early so no foetal pole visible yet,
OR pseudosac which is caused by hormone reaction in ectopic pregnancy

Question 7

What history (3) and examinations (6) are done at antenatal midwife appointment?

Answer 7

History: Physical & mental health, fetal movements. 
Examinations: 
BP, 
urinalysis, 
symphsis-fundal hieght, 
lie and presentation, 
engagement of presenting part, 
fetal heart auscultation

Question 8

List 11 conditions screened for in the 20 week scan.

Answer 8

Edward's syndrome, 
Patau's syndrome, 
anencephaly, 
spina bifida, 
cleft lip, 
congenital diaphragmatic hernia, 
gastroschisis, 
exomphalos, 
congenital heart disease, 
bilateral renal agenesis, 
 lethal skeletal dysplasia

Question 9

The combined test screens for what conditions and between what weeks is it carried out?

Answer 9

Screens for Down’s, Edward’s and Patau’s syndrome and is carried out between 10-14 weeks

Question 10

What is the combined test?

Answer 10

Combined blood test (HCG and PAPP-A),

USS to check nuchal translucency/nuchal thickness

Question 11

The quadruple test screens for what condition and what weeks of pregnancy is it carried out?

Answer 11

Screens for just Down’s syndrome and is carried out between 14-20+6 weeks

Question 12

What is the quadruple test?

Answer 12

Maternal age, gestation and levels of 
bHCG, 
unconjugated estriol (UE3), 
alpha-fetoprotein,
inhibin A

Question 13

Which is more accurate - combined or quadruple test?

Answer 13

Combined more accurate for screening for Down’s syndrome

Question 14

Major structural abnormalities occur in what percentage of pregnancies?

Answer 14

2-3%

Question 15

What is placenta praevia and at what scan is it identified?

Answer 15

Low-lying placenta that covers all or part of the cervix, identified at the anomaly scan (AKA 20 week scan)

Question 16

When are normal pregnancy USS scans?

Answer 16

10-14 weeks (12 week) and 18-21 weeks (20 week)

Question 17

What is the management plan if the placenta is seen to be lying low on anomaly scan?

Answer 17

Placental site is rechecked at 32 weeks by USS, sometimes transvaginal

Question 18

What are 2 conditions that can cause increased nuchal thickness?

Answer 18

Chromosomal abnormalities and fetal heart abnormalities

Question 19

What are the approximate sensitivity and false positive rates for combined test?

Answer 19

95% sensitivity and 5% false positive

Question 20

A value of < what is considered normal NT?

Answer 20

<3.5mm

Question 21

What is CRL and what is it used to measure?

Answer 21

Crown Rump length - the length of the foetus from top of the head to bottom of torso. It’s used in early pregnancy to measure gestation

Question 22

The CRL must be between what mm for first trimester trisomy risk assessment NT test to be carried out?

Answer 22

Between 45 and 84mm

Question 23

What is offered as a secondary screening test if high chance result for any trisomy test?

Answer 23

Non-invasive prenatal testing: analysis of circulating fetal DNA fragments in maternal blood

Question 24

Trisomy assessment >1:150 is high risk. What should be carried out next?

Answer 24

NIPT or CVS/amniocentesis

Question 25

NIPT (AKA cell free fetal DNA (cffDNA)) is accurate from around how many weeks pregnancy?

Answer 25

around 10 weeks

Question 26

cffDNA is less accurate than the combined test for identifying risk of Down's syndrome. True/false?

Answer 26

False - more accurate

Question 27

What is the approximate sensitivity and false positive rate of NIPT? What can cause the false positive rate?

Answer 27

Sensitivity rate: >99% and false positive rate: <0.1%. False positive rate could be caused by placenta having trisomy but not foetus

Question 28

Chorionic villus sampling carries a miscarriage rate of 2%. After how many weeks is it usually performed?

Answer 28

after 12 weeks

Question 29

Aminocentesis carries a miscarriage rate of 1%. After how many weeks is it usually performed?

Answer 29

after 15 weeks

Question 30

What is the difference between sickle cell disease and thalassemias genetically and clinically?

Answer 30

Genetically: sickle cell affected have two abnormal haemoglobin genes whereas thalassemia affected has missing genes

Question 31

Thalassaemia can cause symptoms when there are >2 genes. The severity of anaemia in thalassemias depends on the number of genes missing. True/false?

Answer 31

True

Question 32

What is the worldwide leading cause of maternal death?

Answer 32

Postpartum haemorrhage

Question 33

Maternal aneamia is common and can be caused by what 3 deficiencies? Which is most common?

Answer 33

Iron (most common), folate and B12 deficiency

Question 34

When are mothers screened for anaemia?

Answer 34

Screened at booking and at 28 weeks

Question 35

When are mothers blood group and red cell antibodies status checked?

Answer 35

At booking scan and at 28 weeks

Question 36

When should non-invasive fetal genotyping (of D, C, c, E, e and K antigens) using maternal blood be carried out?

Answer 36

Should be done for relevant antigen when maternal red cell antibodies are present

Question 37

How does Rhesus haemolytic disease develop?

Answer 37

Rhesus -ve mother has rhesus +ve baby, rhesus +ve blood cells can enter mother at delivery or sensitising event, rhesus antibodies produced by mother, rhesus antibodies then attack next pregnancy's red blood cells

Question 38

What can cause fetal hydrops?

Answer 38

Haemolytic disease of the newborn

Question 39

When is Anti-D given to pregnant women?

Answer 39

Given routinely at 28weeks to Rh-ve mothers and after any sensitising event, also given again afer birth if baby Rh+ve

Question 40

List 5 risk factors for gestational diabetes that should be identified at the booking appointment.

Answer 40

1. BMI >30kg.m2 2. previous macrosomic baby weighing >4.5kg 3. previous gestational diabetes 4. FH diabetes (first-degree relative) 5. minor ethnic family origin with high prevalence of diabetes

Question 41

Who should be offered testing for gestational diabetes? What is the diagnostic test?

Answer 41

Women with any one of the 5 risk factors. Test is the 2-hr 75g oral glucose tolerance test. +ve gestational diabetes if woman has either a fasting plasma glucose level of 5.6mmol/l or above OR a 2-hour plasma glucose level of 7.8mmol/L or above

Question 42

What is recommended at each antenatal appointment from 24 weeks pregnancy?

Answer 42

Symphysis fundal height measuring to improve prediction of SGA neonate

Question 43

Who should be referred for USS measurement of fetal size? (2) Which needs serial SFH measurements?

Answer 43

Women with a single SFH which plots below 10th centile or serial measurements which show slow growth AND women who won't be able to accurately measure SFH e.g. BMI>35, fibroids, hydramnios - these need serial SFH measurements

Question 44

List 5 examples of women at high risk of pre-eclampsia.

Answer 44

Women with hypertensive disease in previous pregnancy, CKD, autoimmune disease (e.g. lupus or antiphospholipid), T1/T2 DM, chronic hypertension

Question 45

Women at high risk of pre-eclampsia should be managed how?

Answer 45

Should take 150mg aspirin daily from 12wks to 36 wks

Question 46

List 6 examples of women with moderate risk of pre-eclampsia.

Answer 46

``` First pregnancy, age 40 or above, pregnancy interval >10yrs, BMI of 35kg/m or more, FH pre-eclampsia, multiple pregnancy ```

Question 47

Women with more than one moderate risk of pre-eclampsia are managed how?

Answer 47

Should take 150mg daily from 12 weeks until birth

Question 48

What 4 problems does urinalysis screen for?

Answer 48

UTI, asymptomatic bacteriuria (associated with risk of miscarriage, sepsis), proteinuria (pre-eclampsia) and diabetes

Question 49

In which scan are the following tests carried out? Haemogloinopathies, Hep B & C, HIV, Syphillis, red cell antibodies, anaemia, no. foetuses, viability, PMH, PSH, obstetric Hx, DH, allergies, SH, FH, past mental health history, FGM, BMI. Trisomy screening offered

Answer 49

Booking

Question 50

In which scan are the following tests carried out? Cleft, heart, limb, neural tube & abdo wall defects, lung, brain and urinary tract abnormalities, placental site and diaphragmatic hernia

Answer 50

20wk anomaly scan

Question 51

In which scans are the following tests carried out? | red cell antibodies and anaemia

Answer 51

Booking & 28wk

Question 52

In which scan are the following tests carried out? | BP, urine, macrosomia/IUGR, mental health, abuse and support

Answer 52

All ANC

Question 53

CRL is useful as a measurement of gestational age from 6-13weeks. What is used afterwards?

Answer 53

Head circumference, biparietal diameter and femur length

Question 54

After what maternal age does risk of Down's Syndrome steeply increase?

Answer 54

from age 40