Antenatal Screening

Question 1

Describe morning sickness

Answer 1

Affects around 80-85% of women

Worse in conditions where Human Chorionic gonadotrophin is higher eg. twins, molar pregnancy

Can progress to hyperemesis gravidarum

Question 2

What is hyperemesis gravidarum?

Answer 2

Severe nausea and vomiting in pregnancy, often requiring hospital admission

Question 3

Describe cardiac pregnancy problems

Answer 3

Cardiac output increases by 30-50%

HR increases from 70-90bpm

Palpitations are common

At term blood flow to uterus must exceed 1L/min

Blood pressure drops in second trimester

Question 4

Why does the blood pressure drop in the second trimester?

Answer 4

• expansion of uteroplacental circulation
• fall in systemic vascular resistance
• reduction in blood viscosity
• reduction in sensitivity to angiotensin

BP usually returns to normal in third trimester

Question 5

Describe urinary problems in pregnancy

Answer 5

Increased urine output

• renal plasma flow raises by 25-50%
• GFR increases by 50%
• some urea and creatinine decrease

UTI

• increase in urinary stasis
• hydronephrosis physiological in third trimester and make pyelonephritis more common
• can be assoc. with preterm labour

Question 6

Describe haematology in pregnancy

Answer 6

Plasma volume increases by ~50% and RBC mass by ~25%

Results in drop in haemoglobin by dilution from 133-121g/L

Iron requirements are increased 1g during pregnancy

WBC increases slightly to 9000-12000/uL

Platelet count falls by dilution

Question 7

Respiratory changes in pregnancy

Answer 7

Progesterone reduces CO2

• raised tidal volume
• raised resp rate
• raised plasma pH

O2 consumption rasied by 20%

Plasma PO2 unchanged

Hyperaemia of resp mucus membranes

Question 8

Describe GI changes in pregnancy

Answer 8

Oesophageal peristalsis is reduced

Gastric emptying slows

Cardiac sphincter relaxes

GI motility is reduced due to raised progesterone and reduced motilin

Question 9

What is involved in the ideal pre-pregnancy counselling?

Answer 9

General health measures

• improve diet
• optimise BMI
• reduce alcohol consumption

Smoking cessation advice

Folic acid; 400mcg

Optimise maternal health, consider psychiatric health, previous pregnancy problems

Stop/change unsuitable drugs

Occasionally advise AGAINST pregnancy; i.e. diabetes or epilepsy

Question 10

What previous pregnancy problems should be considered when counselling women about getting pregnant?

Answer 10

Maternal
- Counsel regarding risk of recurrence; c-section, DVT, pre-eclampsia

• actions to reduce recurrence risk; thromboprophylaxis, low dose aspirin

Fetal
- counsel regarding recurrence risk; pre-term delivery, intrauterine growth restriction, fetal abnormality

• actions to reduce recurrence risk; treat infection, high dose folic acid, low dose aspirin

Question 11

What is carried out in a routine antenatal examination?

Answer 11

Routine enquiry; feeling well, movements? (after 20 weeks)

BP; detect evolving hypertension

Urinalysis; protein in urine sign of pre-eclampsia

Abdominal palpation; assess SFH, estimate size of baby, estimate liquid vol, determine foetal presentation, listen to foetal heart

Question 12

What is symphyseal fundal height?

Answer 12

aka SFH

Measured from top of uterus to pubic symphysis and roughly corresponds to gestation age when measured in cms

Question 13

Describe screening for infection in pregnant women

Answer 13

• Hep B; if infected can provide passive and active immunisation for baby
• Syphilis; easily treated with penicillin
• HIV; maternal treatment and careful planning reduces vertical transmission
• MSSU; UTI

Question 14

Describe screening for anaemia and isoimmunisation in pregnancy

Answer 14

Iron deficiency anaemia

Isoimmunisation

• rhesus disease
• anti-c, anti-Kell

Question 15

What is the purpose of the first visit US scan?

Answer 15

• ensure pregnancy viable
• multiple pregnancy
• identify abnormalities incompatible with life
• offer and carry out Down’s Syndrome Screening

Question 16

What is a detailed anomaly scan used for?

Answer 16

• systemic structural review of baby
• not possible to identify all problems
• can identify problems that need intrauterine or postnatal treatment

Question 17

Describe Down’s Syndrome Screening

Answer 17

Overall risk is 1 in 100

Usual cut-off for ‘high risk’ is 1 in 150

Maternal age increases risk;

• 1 in 1667 at 20yrs
• 1 in 30 at 45yrs

Various screening tests available; women and partners must be aware that screening only provides RISK

Further testing to determine if definitively affected

Question 18

Describe first trimester screening for Down’s Syndrome

Answer 18

Carried out at 10-14 weeks gestation

Uses maternal risk factors;

• serum b-hCG
• PAPP-A

Use foetal nuchal translucency

Question 19

What is PAPP-A?

Answer 19

Pregnancy Associated Plasma Protein A

Used for detecting risk of Down’s Syndrome in foetus

Question 20

What is the detection rate for Down’s Syndrome using screening?

Answer 20

Trisomy 21 of ~90%

Question 21

When is NT measurement taken?

Answer 21

Between Crown Rump Lengths of 45-84mm

Question 22

When is further testing offered in response to Down’s Syndrome screening results?

Answer 22

If risk is > 1 in 150

Options are

• CVS
• amniocentesis
• non-invasive prenatal testing

Question 23

When is CVS carried out?

Answer 23

Between 10-14 weeks

~1-2% risk of miscarriage

Question 24

When is amniocentesis carried out?

Answer 24

15 weeks onwards

~1% risk of miscarriage

Question 25

What is non-invasive prenatal testing?

Answer 25

Maternal blood taken

• can detect foetal cell free DNA
• can look for chromosomal trisomies
• if high risk invasive testing still recommended to confirm

Question 26

What is the second trimester US used for?

Answer 26

To detect foetal abnormality

Good test for major structural abnormalities but poor for chromosomal abnormalities