Prenatal Testing

Question 1

CVS

Answer 1

10-12 weeks

earlier Dx leads to safer termination

Technically difficult, especially when placenta is posterior

Fetal loss rate - .5%-1%

Question 2

Amniocentesis

Answer 2

15-16 weeks

technically easier to do

Fetal loss rate - 1:600 - 1:1000

Question 3

Cordocentesis

Answer 3

After 20 weeks

• Need for rapid test results particularly later in pregnancy
• Need to assess fetal hematocrit b/c of isoimmunization or parvovirus

Fetal loss rate - 1%

Question 4

NIPS

Answer 4

After 10 weeks

-T13, T18, T21, sex chr abnormalities, some microdeletions

99% sensitive for T21

Question 5

NT Screen

Answer 5

12-13 weeks

T18, T21

85% sensitive

Question 6

Quadscreen

Answer 6

15-18 weeks

T18, T21, NTD

75-80% for T18, T21
90% for NTD

Question 7

Ultrasound

Answer 7

16-20 weeks

NTD, T13, T18, T21

70% for fetal aneuploidy
99% for NTD

Question 8

Ultrasound markers associated w/ fetal aneuploidy

Answer 8

Absent nasal bone - 20+

Thickened nuchal fold - 18-20

Echogenic bowel - 5-6

Question 9

U/S major structural malformations associated w/ fetal aneuploidy

Answer 9

Cystic hygroma, duodenal atresia, omphalocele, holoprosencephaly, cardiac malformation, NTD

Question 10

U/S major structural malformations associated w/ fetal aneuploidy

cystic hygroma

Answer 10

65%

45,X or T21

Question 11

U/S major structural malformations associated w/ fetal aneuploidy

duodenal atresia

Answer 11

30%

Trisomy 21

Question 12

U/S major structural malformations associated w/ fetal aneuploidy

omphalocele

Answer 12

30%

Trisomies

Question 13

U/S major structural malformations associated w/ fetal aneuploidy

holoprosencephaly

Answer 13

5-10%

Trisomy 13

Question 14

U/S major structural malformations associated w/ fetal aneuploidy

cardiac malformation

Answer 14

5-10%

Trisomies 18 & 21

Question 15

U/S major structural malformations associated w/ fetal aneuploidy

NTD

Answer 15

5-10%

Trisomies