Amniocentesis is a diagnostic prenatal test preformed from 15 weeks of pregnancy onwards to identify genetic disorders. It involves inserting a fine needle through the maternal abdomen into the amniotic sacs, which surrounds and protects the baby, to withdraw a small amount of fluid surrounding the baby. The fluid is called amniotic fluid and contains fetal cells, which are analyzed for chromosomal and, if indicated, specific genetic conditions.

Unlike NIPT or ultrasound markers, amniocentesis provides a definitive diagnosis — it directly examines fetal chromosomes (karyotype/microarray) rather than estimating risk.

It is typically recommended for:

*Women with positive prenatal screening tests such as dual marker, NIPT etc.
*Previous child or previous pregnancy with a genetic disorder
*Advanced maternal age of 35 years or above.
*Significant or multiple ultrasound markers/structural anomalies
*Family history of a genetic condition requiring specific testing
*Couple carrier for a genetic disorder

It is usually performed between 15–20 weeks of gestation and can be done later at any stages of pregnancy if needed. It is not done before 15 weeks due to higher procedure-related risk.

It provides a definitive result rather than a risk estimate and allows parents and clinicians to plan management, further testing, or pregnancy decisions with certainty, rather than probability. The accuracy of these tests are greater than 99%.

Limitations:

Procedure-related miscarriage risk exists, generally cited as approximately 0.1% in experienced hands – this should be discussed with the patient’s own clinician for center-specific and patient health-specific figures.
It is an invasive procedure requiring informed consent and is performed by a trained specialist under ultrasound guidance.
Results (especially full karyotype) can take 1–3 weeks, though rapid FISH/QF-PCR results for common trisomies are often available within 48–72 hours, time taken for report depends on the test performed and can take longer if advanced tests like whole exome sequencing or whole genome sequencing are performed.
It does not detect every possible genetic condition: the specific test ordered (karyotype vs. microarray vs. targeted panel) depending on the provisional diagnosis made or what the screening tests are indicated towards determines what is covered.