Prenatal diagnosis Flashcards
What are the first trimester screening tests?
Combined Test
1- HCG
2- PAPPA
3- Nuchal translucency: measured when CRL is 45-84mm
at 10 - 14 weeks
What are the anomalies that can be suspected using the first trimester combined test?
- Trisomy 21 -> high HCG + low PAPPA
- Trisomy 18 -> low HCG + low PAPPA
What are the second trimester screening tests?
Quad screening at 15-20 weeks
1- maternal serum alpha fetoprotein
2- HCG
3- Inhibin
4- Unconjugated estriol
What are the soft markers that indicate increased risk of having aneuploidies?
First trimester
- increased Nuchal translucency
Second trimester
- D-echogenic bowel
- B-echogenic intracardiac focus
- short femur
- absent fetal nasal bone
What is the relation of first trimester screening with maternal age?
- mothers < 35 years -> trisomy 21 detection rate is 6 - 75%
- mother > 35 years -> detection rate 90%
What are the indicators of trisomy 21 in combined first & second trimester screening tests?
- MSAFP decreased
- HCG increased
- PAPPA decreased
- unconjugated estriol decreased
- inhibin increased
- Nuchal translucency increased
What are the indicators of trisomy 18 in combined first & second trimester screening tests?
- MSAFP decreased
- HCG decreased
- PAPPA decreased
- unconjugated estriol decreased
What are the causes of a high MSAFP?
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
What is the best way to have the highest detection rates?
integrated first & second trimester tests
How is cell free fetal DNA preformed?
DNA fragments from apoptotic trophoblasts
- after 10 weeks
- 99% detection rate
- noninvasive
What screening tests should be done in the preconception period?
- Haemoglobinopathies -> sickle cell disease, thalassamia
- Spinal muscular dystrophy
- Cystic fibrosis
- used for preimplantation diagnosis
- ethnic based carrier screening
What are the invasive diagnostic tests?
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
What are the indications for amniocentesis?
- diagnosis of aneuploidies
- congenital infection
- red cell alloimmunization
What are the indications for cordocentesis?
sampling of fetal blood for
- fetal blood transfusion in RH
- allo immunization
- platelet allo immunization
- karyotyping