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203: Reproductive system, fetal development, pregnancy and birth > Prenatal screening > Flashcards

Prenatal screening Flashcards

1
Q

Purpose of screening

A

Identifies risk of condition/ disease to allow earlier treatment or informed decisions

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2
Q

Preconception screen

A

Diabetic

- Diabetic eye test

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3
Q

Sick cell and thalasesemia screening

A

Screened early

1-10 weeks

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4
Q

Early pregnancy scan

  • When
  • Things looked for
A

10-14 weeks

Viability

  • Any miscarriage?
  • Is the fetus alive?

Accurate dating

  • Uses last menstrual period
  • Crucial for dating of screening tests
  • Avoids inducing labour

Determine chorionicity

  • Mono/di
  • Monochorionic twins require more monitoring and care

Structural abnormalities

Chromosomal scan

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5
Q

Structural abnormalities in early pregnancy scan

A

Spina bifida

Anencephaly

Exomphalos
- Weakened abdominal wall

Gastroschisis
- Bowel outside abdominal wall

Bladder flow obstruction.

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6
Q

Most common trisomies

A

21- Down’s

18- Edward’s

13- Patau’s

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7
Q

Chorionic villus sampling [CVS]

A

Can be conducted from 11 weeks
- Test material from placenta using a needle

Diagnoses trisomy

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8
Q

Amniocentesis

A

Conducted from week 16
- Testing of amniotic fluid

1% risk of miscarriage

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9
Q

Combined screening test

  • When
  • What
A

11 weeks + 2 days
between
14 weeks + 1 day

Combines three modality

  • Maternal age
  • Nuchal translucency
  • Maternal blood test (PAPPA, beta-hCG)
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10
Q

Maternal age screening

A

Older age= increased risk of Down’s significantly.
- Egg cells more likely to have extra chromosome due to increased stress

Also

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11
Q

Nuchal translucency scan

A

Fluid at the back of the neck
- Greater amount of fluid= increased risk of trisomy

Done 11+2 - 14+1 weeks.

Normal
45-84 mm

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12
Q

Free beta-hCG

A

Tends to be higher than average in Down’s

  • Maternal blood tests
  • Done in combined test
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13
Q

PAPP-A

A

Tends to be lower in Down’s

- Maternal blood test done in combined screening

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14
Q

Maternal factors influencing combined screening

A

Maternal age

Ethnicity
- Affects normal level of biomarkers

Smoking

Weight
- Affects levels in blood

Diabetes

Past history of chromosomal abnormality

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15
Q

Fetal factors influencing combined screening

A

IVF

  • frozen embryo, age is based when the egg was harvested
  • Donor egg age considered

Multiple pregnancy
- More than 2 fetus= cannot do accurate screening.

Sex

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16
Q

Combined screening result national cut off

A

1 in 150

151+ letter in 2 weeks
under 150 or lower= call within 3 days

17
Q

Combined screening DR and screening positive rate

A

DR= 82%

SPR= 2.7%

18
Q

Nuchal translucency

  • Description
  • Factors screened for
  • Further investigations
A

Fluid in the back of the neck

> 3.5mm = increased risk of:

  • Chromosomal anomaly
  • Cardiac anomaly
  • Sydromes

If increased, further investigations

  • Karyotyping
  • Fetal cardiac scan
  • Anomaly scan
19
Q

Quadruple test

A

Second trimester serum screening
- 14+2- 20 weeks

Only assesses Down’s

Looks for levels of

  • UE3
  • AFP
  • Inhibin A
  • beta-hCG
20
Q

Quadruple test detection and positive rate

A

DR- 75%

SPR- 5.5%

Monochorionic twins
- 80% DR, 3%

Dichorionic twins
- 40-50% DR, 3% SPR

21
Q

Non-invasive prenatal testing

A

Cell free fetal DNA

  • Placenta sheds fetal DNA
  • Can be detected from 10 weeks in maternal blood
  • Pregnancy specific

over 99% sensitivity for Down’s

Going to be introduced to women with high chance on combined/ quadruple screening
- Singleton pregnancy

22
Q

Exclusions of NIPT

A

Due to risk of false positives

  • Maternal malignancy
  • Multiple pregnancy
  • Blood transfusion within 4 months
  • Organ transplant
  • Vanished twin
  • Known chromosome anomaly
23
Q

NIPT advantages

A

High detection rate

Low screen positive rates

Reduction in invasive diagnostics

24
Q

NIPT disadvantages

A

Not diagnostic

Screen positive test have to be confirmed with invasive test

203: Reproductive system, fetal development, pregnancy and birth (23 decks)

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