A. Amniocentesis – Explanation

The most appropriate test at this gestation would be an amniocentesis.

Amniocentesis
Amniocentesis is an invasive, diagnostic antenatal test. It involves taking a sample
ofamniotic fluid in order to examine fetal cells found in this fluid.
Amniocentesis is an invasive procedure, diagnostic antenatal test involving taking a
20ml sample of amniotic fluid using a transabdominal needle under ultrasound
guidancein order to examine fetal cells found in this fluid. It is offered after screening
tests haveindicated a high risk of fetal abnormality or in women considered to be at high
risk, forexample if above 35 years old.
Amniocentesis is usually performed at 16 weeks and the risk of fetal loss is 0.5-1%.
Thekaryotype results typically take 3 weeks.

Conditions which may be diagnosed
– Neural tube defects (raised AFP levels in the amniotic fluid)
– Chromosomal disorders
– Inborn errors of metabolism

Timing of amniocentesis
– Early (between 12 and 14+6 weeks of gestation):
o This is not recommended, as it is associated with an increased risk ofmiscarriage
– Mid-trimester (between 15 and 18 weeks of gestation):
o This is the most common time for the procedure.
– Third trimester
o May be undertaken for late karyotyping
AMNIOCENTESIS VS CHORIONIC VILLOUS SAMPLING VS NON INVASIVE
PRENATAL TESTING