Antenatal Care and Screening in Pregnancy

Question 1

how is sensitivity of a test assessed?

Answer 1

true positive/(positive + false negative)

Question 2

how is specificity of a test assessed?

Answer 2

true negative/(negative + false positive positive)

Question 3

what history is done at booking appointment (12 weeks)?

Answer 3

PMH
previous pregnancies (including unsuccessful)
social history
DH
surgical history 
allergies
FH
mental health
FGM
- female genital mutilation

Question 4

naegele’s rule?

Answer 4

predicts an estimated due date based on the onset of the woman’s last menstrual period
- add on 9 months and 7 days

Question 5

investigations at 12 week booking appointment?

Answer 5

examination
- height, weight, BP, CVS, abdo exam
haemoglobin
antibodies (rhesus)
syphilis/HIV/Hep B/C
urinalysis (mid stream, culture)
US

Question 6

what is done at normal antenatal management follow up visits?

Answer 6

history
- physical/mental health
- fetal movements
examinations
- BP
- urinalysis
- symphysis - fundal height
- lie and presentation (should be longitudinal with head down at 28 weeks)
- engagement of presenting part (shouldn't happen before 36 weeks)
- fetal heart auscultation

Question 7

when is fetal anomaly scan done?

Answer 7

20 weeks

Question 8

what anomalies are checked for at 20 weeks?

Answer 8

• Spina bifida
• Anencephaly
• Cleft lip
• Heart defects
• renal agenesis
• skeletal dysplasia
• edward’s syndrome (trisomy 18)
• patau’s syndrome (trisomy 13)
• Abdominal wall defects
  ○ Gastroschisis
  ○ Exomphalos
• Placenta previa
  ○ Low lying placenta
  ○ Often only transient
  Talipes equivarus
  several more

Question 9

what is placenta praevia?

Answer 9

when the placenta is low lying in the womb and covers all or part of the entrance to the womb (cervix)
in most women, as the womb grows upwards, the placenta moves with it so that is in a normal position before birth and doesnt cause a problem

Question 10

how is placenta praevia seen?

Answer 10

if an earlier US (18-20 weeks and 6 days) shows placenta extending over cervix, another scan should be offered at 32 weeks
if this scan is abnormal a transvaginal scan should be offered

Question 11

how is down’s syndrome risk assessed?

Answer 11

first trimester
- measure of skin thickness behind neck using US (Nuchal translucency)
measured at 11-13+6 weeks
combined with HCG and PAPP-A
a value < 3.5mm = normal when CRL is between 45-84mm
- higher NT = higher chance of down’s syndrome

Question 12

2nd trimester down’s syndrome screening?

Answer 12

just a blood test at 15-20 weeks

• assay of HCG and AFP
• UE3
• inhibin A
• not as good as first trimester

Question 13

how is overall down’s syndrome risk formulated?

Answer 13

combination of measurements at 1st/2nd trimester screening combined with maternal age and gestation to give a personal risk
requires accurate pregnancy dating and detailed counselling

Question 14

specific diagnostic tests for down’s syndrome?

Answer 14

amniocentesis
- done after 15 weeks
- sample of amniotic fluid
- 1% risk of miscarriage
chorionic villus sampling
- done after 12 weeks
- placenta biopsy
- 2% risk of miscarriage

Question 15

what are the 2 main haemoglobin disorders in pregnancy/foetus?

Answer 15

sickle cell anaemia
thalassemias
both are AR

Question 16

how can fetal anaemia be picked up?

Answer 16

doppler US

shows increased pressure in middle cerebral artery (baby trying to use all the oxygen it has in the brain)

Question 17

types of maternal anaemia?

Answer 17

iron deficiency
folate deficiency
B12 deficiency

Question 18

when is anaemia screened for?

Answer 18

booking (12 weeks) and 28 weeks

Question 19

how does rhesus haemolytic disease develop?

Answer 19

Rh +ve father and Rh -ve mother conceive a child
child is Rh +ve (from father)
at delivery, Rh +ve baby’s blood enters mother’s bloodstream and invasive Rh +ve blood cells cause the production of Rh antibodies in the mother
these antibodies remain in mother’s bloodstream
when a later pregnancy occurs, the Rh antibodies attach the foetus’s blood cells causing Rh disease

Question 20

how can the risk of gestational diabetes be screened?

Answer 20

determine following risk factors at booking appointment
- BMI >30
- previous macrosomic baby weighing 4.5kg or above
- previous gestational diabetes
- family history of diabetes (1st degree relative)
- ethnic minority family origin with high prevalence of diabetes
woman with any one of these risk factors is offered gestational diabetes testing

Question 21

how is gestational diabetes diagnosed?

Answer 21

2 hour 75g OGTT (7.8mmol/litre or above)

fasting plasma glucose (5.6mmol/litre or above)

Question 22

how is foetal growth monitored?

Answer 22

serial measurement of symphysis fundal height (SFH) at each antenatal appointment from 24 weeks
SFH should be plotted on a customised chart rather than a population based chart

Question 23

what SFH warrants further investigation (US)?

Answer 23

women with single SFH which plots below the 10th centile
serial measurements which demonstrate slow or static growth by crossing centiles
women in whom SFH may be inaccurate (BMI >35, large fibroids, hydramnios)

Question 24

who may be at high risk of pre-eclampsia?

Answer 24

hypertensive disease during previous pregnancy
CKD
autoimmune disease (e.g SLE or antiphospholipid syndrome)
diabetes
chronic hypertension
first pregnancy
age 40+
pregnancy interval >10 years
BMI 35+
family history of pre-eclampsia
multiple pregnancy

Question 25

what advice is given to people at high risk of pre-eclampsia?

Answer 25

advised to take 75mg aspirin per day from 12 weeks until birth
- contraindicated in asthma, peptic ulcers etc

Question 26

what is urinalysis used for in pregnancy?

Answer 26

UTI
asymptomatic bacteriuria
PET
diabetes

Question 27

what blood tests are done at 12 weeks (booking)?

Answer 27

syphilis
HIV
Hep B/C
FBC (anaemia)
rhesus status
check blood type/antibodies
check red cell antibodies

Question 28

what is checked on 12 week scan?

Answer 28

viability of foetus
site of pregnancy (potential ectopic)
molar pregnancy
multiple pregnancy
down's syndrome
estimated date of delivery (EDD)
- based on crown rump length

Question 29

what tests are done at 28 weeks?

Answer 29

repeat bloods

- maximise haemoglobin