Chromosome Analysis, Amniotic Fluid

Chromosome analysis of amniotic fluid (amniocentesis) examines fetal cells from the fluid to detect chromosomal abnormalities—trisomies (21, 18, 13), sex‑chromosome aneuploidies, large rearrangements and copy‑number changes. Samples undergo karyotyping, rapid tests (QF‑PCR/FISH) or chromosomal microarray; results take days to about two weeks. It’s offered for abnormal screening or risk factors and carries a small procedure‑related miscarriage risk.

The genetic test done on amniotic fluid is amniocentesis, which collects fetal cells for laboratory analysis. Common analyses are chromosomal karyotyping and chromosomal microarray (CMA) to detect aneuploidies and small deletions/duplications, plus targeted molecular (single‑gene) testing when indicated. It’s typically performed after 15 weeks’ gestation; results range from rapid screens to 1–2 weeks for full reports.

Amniotic fluid analysis typically includes genetic testing (karyotype, chromosomal microarray, FISH), biochemical assays (alpha‑fetoprotein and acetylcholinesterase for neural‑tube defects), fetal lung maturity tests (lecithin/sphingomyelin ratio, phosphatidylglycerol), infection testing (culture and PCR for TORCH organisms), and bilirubin/hemoglobin evaluation for hemolytic disease. Cytology, metabolic screens, and targeted DNA sequencing may be added when indicated.

Yes. Amniocentesis analyzes fetal cells in amniotic fluid to provide a diagnostic chromosome study (karyotype) and can confirm Down syndrome (Trisomy 21) with very high accuracy. It’s typically performed around 15–20 weeks when screening suggests increased risk. The procedure is invasive and carries a small miscarriage risk, so it’s offered after counseling and positive noninvasive screening.

Chromosome analysis (karyotype) identifies sex chromosomes—typically XX indicates genetic female and XY genetic male—but it does not determine a person’s gender identity. Some people have variations (for example Turner syndrome, Klinefelter syndrome, mosaicism or SRY translocation) or intersex conditions where chromosomal sex, physical characteristics, and gender identity may differ. It shows chromosomal pattern, not identity.

Yes. Amniotic fluid contains fetal cells shed from the baby’s skin, respiratory and urinary tracts, and those cells carry the baby’s DNA. Amniocentesis collects this fluid to analyze fetal genetic material. The fluid also contains small amounts of cell‑free fetal DNA. Genetic testing on amniotic fluid can detect chromosomal abnormalities and certain inherited conditions, usually done in the second trimester.