Amniocentesis

Question 1

What is risk of miscarriage with amniocentesis?

Answer 1

0.5-1%.

Question 2

What gestation is amniocentesis carries out?

Answer 2

Approx. 15wks

Question 3

What cells make up A/F sample?

Answer 3

Heterogeneous: derived from FETAL tissue;
Lungs, urinary tract & skin, 25% epithelial, 15% fibroblasts, extra-embryonic membranes & amniocytes (65%).
More accurate representation of fetal karyotyping than CVS.

Question 4

% of mosaicism in amniocentesis?

Answer 4

0.1-0.3%

Question 5

What are the 3 levels of mosaicism?

Answer 5

• Level 1: paeudomosaicism (cultural artefact) - a single abnormal cell.
• Level 2: 2 or more cells with same abnormality seen in one culture. Almost always pseudomosaicism.
• Level 3: 2 or more cells with same abnormality diatribes over 2 or more independent cultures. Likely true mosaicism present in fetal tissues.