Prenatal diagnosis Flashcards

1
Q

What are the first trimester screening tests?

A

Combined Test
1- HCG
2- PAPPA
3- Nuchal translucency: measured when CRL is 45-84mm

at 10 - 14 weeks

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2
Q

What are the anomalies that can be suspected using the first trimester combined test?

A
  • Trisomy 21 -> high HCG + low PAPPA
  • Trisomy 18 -> low HCG + low PAPPA
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3
Q

What are the second trimester screening tests?

A

Quad screening at 15-20 weeks
1- maternal serum alpha fetoprotein
2- HCG
3- Inhibin
4- Unconjugated estriol

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4
Q

What are the soft markers that indicate increased risk of having aneuploidies?

A

First trimester
- increased Nuchal translucency

Second trimester
- D-echogenic bowel
- B-echogenic intracardiac focus
- short femur
- absent fetal nasal bone

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5
Q

What is the relation of first trimester screening with maternal age?

A
  • mothers < 35 years -> trisomy 21 detection rate is 6 - 75%
  • mother > 35 years -> detection rate 90%
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6
Q

What are the indicators of trisomy 21 in combined first & second trimester screening tests?

A
  • MSAFP decreased
  • HCG increased
  • PAPPA decreased
  • unconjugated estriol decreased
  • inhibin increased
  • Nuchal translucency increased
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7
Q

What are the indicators of trisomy 18 in combined first & second trimester screening tests?

A
  • MSAFP decreased
  • HCG decreased
  • PAPPA decreased
  • unconjugated estriol decreased
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8
Q

What are the causes of a high MSAFP?

A

1- underestimated gestational age
2- multifetal gestation
3- fetal death
4- neural-tube defect
5- esophageal or intestinal obstruction
6- liver necrosis
7- renal abnormalities: polycystic kidneys, renal agenesis, congenital nephrosis, urinary tract obstruction
8- placental abruption
9- oligohydramnios
10- preeclampsia
11- fetal-growth restriction

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9
Q

What is the best way to have the highest detection rates?

A

integrated first & second trimester tests

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10
Q

How is cell free fetal DNA preformed?

A

DNA fragments from apoptotic trophoblasts
- after 10 weeks
- 99% detection rate
- noninvasive

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11
Q

What screening tests should be done in the preconception period?

A
  • Haemoglobinopathies -> sickle cell disease, thalassamia
  • Spinal muscular dystrophy
  • Cystic fibrosis
  • used for preimplantation diagnosis
  • ethnic based carrier screening
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12
Q

What are the invasive diagnostic tests?

A

Chorionic villus sampling
- First trimester -> 10-13 weeks
- karyotyping
- transcervical or transabdominal
- risk of miscarriage & limb reduction defects

Amniocentesis
- Second trimester -> 15-20 weeks
- transabdominal
- risk of pregnancy loss

GIVE ANTI-D in Rh -ive moms AFTER BOTH

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13
Q

What are the indications for amniocentesis?

A
  • diagnosis of aneuploidies
  • congenital infection
  • red cell alloimmunization
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14
Q

What are the indications for cordocentesis?

A

sampling of fetal blood for
- fetal blood transfusion in RH
- allo immunization
- platelet allo immunization
- karyotyping

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