3: Antenatal care and screening in pregnancy

Question 1

When are the first, second and third trimesters?

Answer 1

1st trimester - 1 to 12 weeks

2nd trimester - 13 to 28 weeks

3rd trimester - 29 to 40 weeks

Question 2

When is antenatal care given?

Answer 2

Before birth

Question 3

What is the sensitivity of a test?

Answer 3

Proportion of people with a disease which are detected by the test

i.e test positives / (test positives + false negatives)

Question 4

What is the specificity of a test?

Answer 4

Proportion of patients without a disease who are identified by a test

i.e true negatives / (true negatives + false positives)

Question 5

How is sensitivity calculated?

Answer 5

Sensitivity = (True positives) / (True positives + False negatives)

Question 6

How is specificity calculated?

Answer 6

Specificity = (True negatives) / (True negatives + False positives)

Question 7

What is the positive / negative predictive value of a test?

Answer 7

Proportion of positives/negatives who are actually true

e.g PPV = (True positives) / (True positives + False positives)

gives you an idea of how reliable a test is

Question 8

Screening tests tend to be used to rule diseases ___.

Answer 8

rule diseases out

wide variety of diseases can be screened for, then if any of them are positive, a diagnostic test can be performed

Question 9

When are ultrasound scans carried out in pregnancy?

Answer 9

12 weeks

20 weeks - more detailed one

To test for structural abnormalities e.g those seen in Down’s syndrome

Question 10

What is Naegele’s rule for calculating a woman’s due date?

Answer 10

Take date of last period

Add on nine months and seven days i.e 280 days

Question 11

What are some early blood tests done in antenatal care?

Answer 11

Hb - for sickle cell anaemia anaemia

Blood group

Rhesus antibodies

STIs - syphilis, HIV, Hepatitis B & C

Question 12

What are the steps of antenatal abdominal examination?

Answer 12

Inspect

Palpate - fundus, fundal height, walls for foetal lie and presentation, ballot the presenting part

Auscultate - foetal heart

Question 13

What vital signs and tests are routine at antenatal appointments?

Answer 13

HR, BP, BMI

BG

Urinalysis

Question 14

What is the difference between the lie and presentation of a foetus?

Answer 14

Lie - baby’s position in the womb i.e longitudinal or transverse

Presentation - what part of the baby is most inferior i.e cephalic (head) or breech (feet)

Question 15

What is a normal foetal heart rate?

Answer 15

120 - 160 bpm

Question 16

How is fundal height measured?

Answer 16

Fundus of uterus to Pubic symphysis

Question 17

What is the purpose of antenatal ultrasound testing?

Answer 17

To assess the structure of a foetus for abnormalities and treat them where possible

Question 18

What is placenta praevia?

Answer 18

Placenta lies low in the uterus, obstructing the opening of the cervix

Question 19

How can placenta praevia be detected?

What are the symptoms?

Answer 19

Ultrasound scan

Bleeding

Question 20

Which genetic disorder is screened for in all pregnant women?

Answer 20

Down’s syndrome

Question 21

What should couples be asked before screening for Down’s syndrome is carried out?

Answer 21

Are you sure you want to know?

Have you considered what you would do if positive (i.e keep the baby or termination)?

Question 22

If a baby having Down’s syndrome would make no difference to their parents, should the mother have a screening test?

Answer 22

Arguably no, it makes no difference

Question 23

How does maternal age influence the risk of trisomy 21?

Answer 23

As maternal age increases, risk of trisomy 21 increases

Question 24

Which measurement on foetal ultrasound is used to estimate gestational age?

Answer 24

Crown-rump length

Question 25

Which measurement on foetal ultrasound is used as a predictor for Down’s syndrome?

Answer 25

Nuchal thickness / frequency (NT or NF)

Question 26

What is a normal value for nuchal thickness?

Answer 26

< 3.5 mm

Question 27

A nuchal thickness > ___ mm is suggestive of Down’s syndrome.

Answer 27

> 3.5 mm

Question 28

Which serology tests can be used along with maternal age and nuchal thickness to calculate the risk of Down’s syndrome?

Answer 28

HCG (will be increased)

AFP (will be reduced)

PAPP-A (will be reduced)

Question 29

Apart from ultrasound and serology, what sampling tests can be used to diagnose genetic disorders?

From what point in gestation can they be done?

Answer 29

NIPT (non-invasive prenatal testing) from 8 weeks

Chorionic villus sampling from 12 weeks

Amniocentesis from 16 weeks

Question 30

What is the risk carried alongside chorionic villus sampling and amniocentesis?

Answer 30

Miscarriage

Tiny percentage but still a risk

Question 31

What are two haemoglobin disorders which are tested for in antenatal care?

Answer 31

Sickle cell anaemia

Thalassaemia

Question 32

Although it is important to screen for anaemia in babies, who else might develop it before or after pregnancy?

Answer 32

The mother

Question 33

Which disease, involving antibodies, can cause anaemia and jaundice in a baby?

Answer 33

Rhesus disease

Question 34

Which psychiatric disorders should be screened for in antenatal care?

Answer 34

Post-partum depression

Post-partum psychosis

Question 35

Which endocrine disease should be screened for in antenatal care?

Answer 35

Gestational diabetes

Question 36

What are the risks to a baby following birth if the mother has untreated gestational diabetes?

Answer 36

Macrosomia OR Small-for-dates

Hypoglycaemia

Stillbirth

Question 37

How can foetal growth be assessed?

Answer 37

Measurement of fundal height

Ultrasound scanning

Question 38

If a woman is thought to be at risk of pre-eclampsia, what drug are they asked to take?

Answer 38

75mg aspirin

Daily from 12 weeks until birth

Question 39

Why are pregnant women routinely given a urinalysis?

Answer 39

To detect:

UTI

Asymptomatic bacteruria (which is treated with antibiotics in pregnant women)

Diabetes

Question 40

Why is asymptomatic bacteruria treated in pregnant women?

Answer 40

30-40% go on to develop a UTI