Fluorescence In Situ Hybridization (FISH) for Chromosome 12 Aneuploidy Detection (Amniotic Fluid)

Why This Test Is Done

Your healthcare provider may recommend this test if you’re at higher risk for chromosomal conditions, such as having a family history of genetic disorders, being over age 35, or experiencing complications like miscarriage or recurrent pregnancy loss. It’s also used in prenatal testing when certain ultrasound findings suggest a possible chromosomal issue.

How the Test Works

A small amount of amniotic fluid is collected through a procedure called an amniocentesis. The fluid is then analyzed using FISH to detect specific genetic material (chromosome 12) that may be duplicated or missing. Fluorescent probes light up certain parts of the chromosomes under a microscope, helping identify abnormalities.

What to Expect Before the Test

You’ll typically schedule the procedure between weeks 15 and 20 of pregnancy. You’ll receive local anesthesia, and the provider will insert a needle into your abdomen to collect fluid. The procedure takes about 10–15 minutes and is generally safe but may cause mild cramping or spotting.

What to Expect After the Test

Most women return home the same day. You may experience mild discomfort or spotting for a day or two. Avoid strenuous activity for 24 hours. Your results will be reviewed by a genetic counselor or specialist.