Amniocentesis is an invasive prenatal test usually performed between 16 and 20 weeks of pregnancy, although it can be performed later if there is an indication. Although it used to also be performed even earlier in the second trimester, this is no longer recommended as there is a higher risk of miscarriage and other complications. When it is performed during the optimum time frame, the risk of miscarriage, as well as other complications such as fetal or maternal injury, infection, and preterm labor, is small.

Am amniocentesis involves using a thin needle to take a small sample of the amniotic fluid from within the amniotic sac. Ultrasound guidance is used throughout the procedure. The procedure takes a few minutes to perform, and most women report that it is painless, although others may experience cramping or pressure within the uterus. Any discomfort typically is gone within a few hours following the procedure.

The results of an amniocentesis are considered to be nearly 100% accurate for chromosome abnormalities, although there may be technical difficulties that prevent proper collection of amniotic fluid and cells. Results are available within 7-10 calendar days following the procedure. After an amniocentesis, we advise our patients to go home and relax for the remainder of the day. The following day, patients can resume their normal activities unless otherwise directed by their doctor.

Amniocentesis is often used when the mother is age 35 or older, has a high-risk screen, an abnormality on ultrasound, or if any inherited conditions run in either of the parents’ families.  It is typically used only to diagnose chromosome conditions such as Down syndrome, trisomy 18, and trisomy 13. If indicated, however, it can be used to test for many other conditions. These conditions include, but are not limited to: spina bifida and other neural tube defects, cystic fibrosis, sickle cell disease, fragile X syndrome, spinal muscular atrophy, Tay-Sachs disease, and hemophilia.

Additional testing, called a microarray, can be performed on the amniocentesis at the patient’s request and can detect hundreds of additional genetic disorders. Go to for more information.

Center for Fetal Medicine

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6310 San Vicente Blvd, Suite 520 Los Angeles, CA 90048 | 323.857.1952