screening in pregnancy

Define screening?

Process of surveying a population using a specific marker / markers with presumptive identification of disease

If a patient is identified with a positive finding during screening, what’s next?

Referred them for a diagnostic test

What is the aim of screening?

Identify the individuals in the population at higher risk for a particular disorder

What is screening and diagnosis aimed at? (2)

Screening > applicable to a population

Diagnosis > applicable to an individual patient level

What should the ideal screening test be based on?

A disorder/ disease that has a significant burden on the health system

What are the advantages of screening tests? (5)

1. Good sensitivity and specificity

2. Test is valid and reliable

3. Cheap and easy to perform

4. Sage and acceptable to patients

5. Cost effective

In disease testing what is A,B,C,D ?

A- true positive

B- false positive

C- false negative

D- true negative

Define sensitivity

The ability to correctly identify people who have a condition (high detection rate)

What is the equation of sensitivity ?

True positive / true postive + false negative

Define specificity

The test’s ability to correctly identify people who do not have the condition. (Test is negative)

What is the equation of specificity?

True negative / false positive + true negative

Define positive predictive value

Is the test is positive then the patient has the disease

What is the equation of positive predictive value?

True positive / true positive + false positive

Define negative predictive value

Is the test is negative then the subject does not have the disease

What is the equation of the negative predictive value?

True negative / false negative + true negative

What properties make a good screening test? (3)

1. High sensitivity

2. High specificity

3. Low false positive rate

What does the ideal perinatal screening test aim to do?

Identify common of very NB congenital disorders

What are the properties of an ideal perinatal screening test? (5)

1. Cost effective and easy to perform

2. High detection rate & low false positive rate

3. Reliable and reproducible

4. Screen for a disorder for which there’s a diagnostic test

5. There’s early detection and intervention for the condition if screen is positive

What are the benefits of counselling?

1. Clear and complete information

2. Informed preference based decision

3. No directive

4. Different types > group, individual, written information

Define aneuploidy screening

A safe medical test done to check if a baby has a high / low risk of having an abnormal number of chromosomes

Which condition is the most common aneuploidy among live births? Which impairment does it cause?

Trisomy 21 - Down syndrome

Mental impairment

Who describes and published the accurate description of Down syndrome in 1866?

John Langdon Down

Who discovered which chromosome was responsible in Down syndrome in 1959?

Jerome Lejeune

Down syndrome is due to which failures?

1. Nondisjunction> failure of linked chromosomes to separate properly during cell division

2. Translocation

What does the risk of Down syndrome correlate with?

Increasing with advanced maternal age > risk at 20 is 1min 1070 vs risk at 44 is 1 in 20

What is screening important to detect Down syndrome? (2)

1. Burden on affected individual and family

2. Prenatal diagnosis gives parents options > TOP, opportunity to plan delivery of affected child

During which weeks is the first trimester screening tests done?

10 -14 weeks

What are the 2 protein and hormone markers measured in the first-r=trimester blood test ad part of the maternal serum screening?

1. PAPP-A > Pregnancy associated plasma protein A > a protein made by the development placenta

2. BHCG > Beta Human Chorionic Gonadotropin > a hormone produced by the placenta

*done at 10 weeks

During an ultrasound which markers are used? (4)

1. Crown-Rump Length > 45-84 mm (head to buttock, most accurate way to determine the gestational age during 1st trimester

2. Nuchal translucency > Measures fluid-filled spaces at the back of the developing fetuses neck for genetic and structural differences

3. Nasal bone, ductus venous flow, tricuspid regurgitation

4. Cell free DNA -NIPT > cell free fetal DNA circulating in a pregnant person’s bloodstream

During the second trimester (15-20 weeks), what is the triple test?

1. AFP > alpha-fetoprotein, tumour marker & liver health (hep B,C)

2. Unconjugated estriol > estrogen hormone produced by the placenta and fetus

3. hCG

What is the quadruple test during the second trimester?

1. AFP

2. Unconjugated estriol

3. hCG

4. Inhibin

During the second trimester what could indicative of abnormality on ultrasound finding? (6)

1. Absent / hypoplastic nasal bone

2. Thickened nuchal fold

3. Short femur / humerus

4. Pyelectasis > mild swelling of the renal pelvis

5. Echogenic bowel

6. Echogenic cardiac focus

Which test do we use for diagnostic testing in the first trimester?

CVS - chorionic villus sampling

Which tests do we use for diagnostic testing in the second trimester? (4)

Amniocentesis > QR PCR ,FISH , Full karyotyping

During diagnostic testing what’s very important to remember? Complications? (6)

Counselling for the parents - procedure risk, miscarriage, infection, HIV, spontaneous rupture of membrane

A medical TOP can be done up to how many weeks?

24 weeks (follow up must be done)

If the parents decide to keep the baby with abnormalities how can you monitor this pregnancy? (3)

1. Detailed anatomy ultrasound

2. Fetal echocardiogram

3. Growth scan

*diagnose structural abnormalities such as VSD, ASD, duodenal atresia

Which types of diabetes are pre-existing ? (2)

Type 1 and type 2

What is it called when diabetes occurs during pregnancy?

Gestational diabetes mellitus

Which mother’s fall in the category of high risk screening?

1. AMA >35 yrs

2. First degree relatives with diabetes mellitus

3. Previous gestational diabetes mellitus

4. Obese

5. Previous unexplained stillbirth

6. Previous intrauterine fetal demise

How does the oral glucose tolerance test work? (4)

Patient should fast for 8-12 hours before the test

Bloods are draw line to check fasting blood sugars

A liquid containing 75 grams of glucose is taken within 5 mins

Blood are drawn at 1 hour & 2 hours

When is gestational diabetes classified?

When one / more value is abnormal (fasting, 1hour, 2 hour)

What are the cut-off values for diagnosing gestational diabetes? (3)

1. Fasting P-gluosce is >5.1 mmol/L

2. P-glucose 1 hour is >10 mmol/L

3. P-glucose 2 hours is >8.5 mmol/L

What is the fasting & random glucose in overt diabetes mellitus (first diagnosed during pregnancy) ?

Fasting 7.0 mmol/L

Random glucose 11.1 mmol/L

What is the management for gestational diabetes mellitus? (5)

1. Diet

2. Oral hypoglycaemias

3. Detailed anatomy scan in infant

4. Regular antenatal visits including ultrasound for fetal wellbeing, growth, AFI, Doppler

5. Elective delivery at 38 weeks

For type 2 diabetes what should we also check for? (3)

End organ damage > renal ultrasound, retinopathy & neuropathy

What can you add if the diabetes type 2 is still uncontrolled on diet and oral agents? (3)

Insulin + aspirin + folic acid

In type 2 diabetes what should you also screen for ?

Infection especially urinary tract