Definition

Amniocentesis is the removal of a small amount of fluid from the uterus (womb). This fluid, called amniotic fluid, surrounds a developing baby.

Amniocentesis

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Reasons for Procedure

Amniocentesis is most often done to see if there is an abnormality in your baby's genes (DNA). It can also be done to see if your baby is developing rightly.

Some things may make your doctor more concerned that there may be a problem:

  • Mother is over 35 years old (at the time of delivery)
  • Family history of chromosome abnormality
  • Family history of inherited disorder
  • Family history of neural tube defect (problems in spine and brain growth, such as spina bifida or anencephaly)
  • To determine whether the baby's lungs are mature
  • Abnormal results from earlier blood screening test, such as maternal serum alpha-fetoprotein (AFP)

Depending on your risk factors, the cells are tested for:

  • Chromosome abnormalities—This testing detects most chromosome abnormalities. The results are usually ready within 14 days. Missing or extra chromosomes lead to physical birth defects and mental retardation. The most common is Down syndrome. This is caused by an extra #21 chromosome.
  • Inherited genetic diseases—Test results are usually ready in 1-5 weeks. Examples include:

Possible Complications

If you are planning to have an amniocentesis, your doctor will review a list of possible complications, which may include:

  • Miscarriage—less than 1% risk
  • Bleeding, cramping, and leaking fluid from the vagina
  • Infection
  • Harm to the fetus by needle (rare)
  • Mixing of blood if you and your baby have different blood types
  • Need for repeat testing

Factors that may increase the risk of complications include:

Be sure to discuss these risks with your doctor before the procedure.

What to Expect

Anesthesia

Your doctor may give you local anesthesia. This numbs a small area.

Description of the Procedure

This is usually done when you are 16 weeks pregnant.

First, your doctor will do an ultrasound to choose a safe spot to insert the needle. Your abdomen will be cleaned. Next, the doctor will insert a very thin needle through the abdomen into the uterus. A few teaspoons of amniotic fluid will be taken out. After the needle is removed, the doctor will make sure that your baby's heartbeat is normal. In most cases, an ultrasound will be used throughout the procedure.

How Long Will It Take?

About 45 minutes—20 minutes to locate the fetus and insert the needle, 5 minutes to withdraw the fluid, 15-20 minutes to rest after the procedure

Will It Hurt?

You may feel cramping when the needle enters your uterus. You may also feel pressure when the fluid is withdrawn.

Post-procedure Care

When you return home after the procedure, do the following to help ensure a smooth recovery:

  • For the first few hours, avoid physical stress.
  • Rest for the first 24 hours. Avoid heavy exercise and sexual activity for 24 hours.
  • Be sure to follow your doctor's instructions.

Most women will have normal results.

Call Your Doctor

After arriving home, contact your doctor if any of the following occurs:

  • Signs of infection, including fever and chills
  • Nausea or vomiting
  • Pain or cramping in the lower abdomen or shoulder
  • Vaginal bleeding or a loss of fluid from the vagina
  • Redness, swelling, increasing pain, excessive bleeding, or discharge from the amniocentesis site
  • New, unexplained symptoms

In case of an emergency, call 911.