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Amniocentesis, sometimes called amnio for short, is a common prenatal test that is used to diagnose birth defects and genetic conditions, such as Down syndrome and open neural tube defects.

During amniocentesis, your physician obtains a small sample of the amniotic fluid surrounding your baby. The test is usually performed by a specialist in maternal-fetal medicine.

Amniocentesis is offered to women who are 35 or older or whose babies are at increased risk for chromosomal abnormalities. The test is generally performed between the 15th and 20th weeks of your pregnancy.

What to Expect

Before the procedure, your abdomen will be cleansed with antiseptic and you may receive a local anesthetic to numb your skin.

During the procedure, your physician will use an ultrasound to help guide a long, thin needle through your abdomen and into your amniotic sac to withdraw a small sample of fluid. If you are the mother of multiples, a fluid sample must be taken from each amniotic sac.

After the procedure, the fluid will be taken to a laboratory for analysis. You should avoid strenuous activity for at least 24 hours after amniocentesis, and you may feel some cramping. You will receive your test results in about two weeks

Chorionic Villus Sampling

Chorionic villus sampling (CVS) is a prenatal test performed in the first trimester in which a sample of chorionic villi, or pieces of placental tissue that share your baby’s genetic makeup, are removed for testing. CVS can reveal whether your baby has a chromosomal condition, such as Down syndrome, Trisomy 13 or Trisomy 18, or other genetic conditions, such as cystic fibrosis.

CVS may be performed for a number of reasons, including:

  • You had a positive result on a prenatal screening test, such as Non-Invasive Prenatal Testing (NIPT) or First Trimester Screening.
  • You had a chromosomal condition in a previous pregnancy.
  • You are age 35 or older.
  • You have a family history of a specific genetic condition, or you or your partner is a known carrier of a genetic condition.

CVS carries a risk of miscarriage (about 1 in 100[LO1]* ) and other complications. Your health care provider will discuss these risks with you.

About the Procedure

Before the procedure, you will need to have a full bladder. Be sure to drink plenty of fluids before your appointment.

During the procedure, your health care provider will use ultrasound to determine your baby’s position and to guide a thin, hollow tube called a catheter that will be used to take a small tissue sample. After cleansing your vagina and cervix with antiseptic, your health care provider will open your vagina with a speculum and insert the catheter through your cervix. When the catheter reaches your placenta, gentle suction will be used to remove a small tissue sample.

You may experience some cramping when the tissue sample is removed. The procedure typically takes about 30 minutes.

After the procedure, the tissue sample will be analyzed in a lab. You will receive your test results in about two weeks.

You may experience a small amount of vaginal bleeding immediately after the procedure and should plan to rest for the remainder of the day.

Call your health care provider immediately if you experience symptoms including:

  • Fluid leaking from your vagina
  • Heavy bleeding
  • Fever
  • Uterine contractions


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