Amniocentesis

image001 Some pregnant women will need to have an amniocentesis during pregnancy to rule out genetic or inherited birth defects. This test is usually done after blood testing comes back abnormal for a possible genetic defect. The test does come with some risks, but most mothers and babies do just fine. Mothers are told to rest for a few days and most often have no complications. 

What Is an Amniocentesis?

Amniocentesis testing involves the doctor removing some of your amniotic fluid from the amniotic sac. The amniotic fluid has cells from your baby in it and these cells can be used to obtain your baby’s genetic details. After the doctor removes the fluid with a needle, it is placed in a vial and sent to the lab to look for abnormal cells. The good thing about amniocentesis is that you can obtain a diagnosis and know for sure if your baby is going to have a genetic defect. An amniocentesis test can also tell you if your baby is a boy or girl.

Doctors normally do amniocentesis after the 15th week of pregnancy. Before the 15th week, there is not enough amniotic fluid to perform the test and there are also risks of causing a birth defect from the procedure. If there is not enough fluid, there is not enough of your baby’s cells to get an accurate diagnosis.

Amniocentesis is not usually done in the third or last trimester of pregnancy, but they may be done if an ultrasound done late in pregnancy has abnormalities. They can also do an amniocentesis later in pregnancy to drain off amniotic fluid if you have more than usual. This condition is also known as polyhdramnios.

Look for more information about an amniocentesis? Check out the video below:

Why Should I Take an Amniocentesis?

In your first trimester of pregnancy, blood tests will be drawn to check for markers of certain chromosomal abnormalities. It is normally followed up with an ultrasound scan and if both show signs of a possible abnormality, then an amniocentesis is done for a positive diagnosis. These defects include Down’s syndrome and other types of Trisomy.

The amniocentesis test has some risks to the pregnancy, so it is only done if preliminary tests show a possible defect or the mother is in a high risk category due to:

  • Children in the family with birth defects
  • Advanced age over 35 years old
  • Abnormalities seen on ultrasound
  • Abnormalities on blood screening

An amniocentesis cannot catch every birth defect, but can detect with surprising accuracy:

  • Cystic Fibrosis
  • Down syndrome
  • Sickle cell anemia
  • Muscular dystrophy
  • Tay-Sachs disease
  • Spinal bifida
  • Anencephaly
  • Lung development in the last trimester of pregnancy if your baby may be premature.
  • Amniotic fluid infections

It may not find the following: heart defects, cleft lip, cleft palate or club foot. The ultrasound done during the test may pick them up, but the sampling of fluid will not. In addition, the sex of the baby will be known as a result of the test and is even more accurate than ultrasound.

How Is an Amniocentesis Performed?

This procedure is usually done in a room of the birthing center to be able to handle any complications that may arise. It is actually pretty quick and easy. Here are the steps:

Steps

Descriptions

Put on a gown

You will be taken into a room and asked to put on a gown and lie back in bed.

Receive a local anesthetic

The doctor will come in with an ultrasound machine and offer a local anesthetic to the area if you want to use it. The procedure is usually not very painful for most women.

Take an ultrasound

The doctor will place some ultrasound gel on your belly and look at the baby. He will then find a good size pool of amniotic fluid that he can safely pull out without harming your baby or the placenta.

Insert a needle

Once he or she finds a good spot, a thin needle will be inserted through the wall of your abdomen into the amniotic sac. The doctor will take a small sample of fluid, which contains your baby’s cells and genetic makeup. The lab will be able to determine if there are any genetic issues with your baby.

Have an anti-D injection if necessary

If you fall into the RhD negative group and your baby is RhD positive then you may have to have an anti-D injection to prevent rejection of the baby when your cells mix.

Check and watch

After the procedure, a nurse will check your baby’s heartbeat and watch you both for a little while before you are released to go home.

Rest for a few days

You may be told to rest and take it easy for a few days after the procedure.

What Risks Are Associated with an Amniocentesis?

There are some risks associated with having an amniocentesis. While it is important to take them into consideration, sometimes doctors may feel the benefits of finding out a severe disability in your baby outweigh the risks. In this way, you can begin planning for your baby’s special needs after delivery. Here is a list of possible risks:

Risks

Descriptions

Miscarriage

An amniocentesis done in the second-trimester of pregnancy increases the risk of miscarriage very slightly. The risk averages miscarriage every 1 in 300 or 1 in 500 procedures. If your amniocentesis is done prior to your 1th week of pregnancy, the risk is slightly higher.

Injury from the needle

It is possible that your baby is moving and gets in the way of the needle, but there are not usually any life threatening injuries.

Amniotic fluid leaks

The needle hole will seal up quickly after the procedure, but there is a rare chance you may experience some leaking out of your vagina afterwards. If this continues, your baby may have some problems.

Rh incompatibility

If your baby is Rh positive and you are Rh negative, your baby’s blood mixing with yours could cause you to fight off baby’s cells. Rh negative mothers need to have Rh immunoglobulin injections to prevent this occurrence.

Infection

While this risk is very rare, it is possible to acquire an infection in your uterus after amniocentesis.

Infections passed to your baby

A mother who has hepatitis C, HIV or toxoplasmosis may pass this infection to her baby while having amniocentesis.

You will be the one making the final decision to have an amniocentesis, so it is important to be informed of the risks. However, if you are at risk for having a baby with a genetic defect, an amniocentesis can help the doctor manage your pregnancy and help you plan after your baby’s delivery. Ask your doctor and any genetic professionals to help you with understanding the procedure thoroughly, so you can make the best decision possible.

There are some instances when you might wish to say “no” to a routine amniocentesis. If you need to deliver a baby prematurely, an amniocentesis may be offered to tell you if the baby’s lungs are mature or not. Having the test done will not change the outcome, but can help you and your doctor plan for what will be done if your baby is born with respiratory issues. Again, this decision will be entirely up to you.

What About the Results?

The results of amniocentesis may take a little time to come back to your doctor. After the fluid is withdrawn, it will be sent to a laboratory that deals with genetic testing for results. If your doctor only orders the usual PCR or polymerase chain reaction test for chromosome counting then the test will be back in about 3 days depending on the lab. The PCR test can tell your doctor whether your baby has Down syndrome if there are an abnormal number of pairs. If your doctor orders a culture of the fluid, the results could take about 3 weeks to come back. Cultures give a more detailed view of the cell structure or karyotyped.

When you go to the hospital for your procedure, the nurse who does your discharge should let you know when and how you will get your results from the doctor. You usually need to contact your doctor directly and not the hospital or the lab as they are not allowed to give results over the phone.

While you are waiting, just know that most babies’ amniocentesis results come back normal and you may not need any further testing after an amniocentesis. In the rare instance, there is a problem, you will be sent to a doctor that specializes in fetal medicine. One of the first things they will discuss, although sensitive, is if you want to continue your pregnancy. Again, this is something only you can decide as parents. Regardless of what you choose, you will find very supportive medical staff to help you along the way. If you do continue the pregnancy, there are many specialists to help care for your baby during pregnancy and after it is born.

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