St. Luke’s Maternal Fetal Medicine

Amniocentesis

This information is provided by St. Luke’s Medical Center to help answer some basic questions about prenatal diagnosis and amniocentesis. If you are uncertain about whether to have the procedure or if you have more questions, we encourage you to discuss these issues with your health care provider.

What is an amniocentesis?
During an amniocentesis, a thin needle is put through a woman’s abdomen and into the fluid-filled sac around the developing baby. A small amount of fluid is taken out through the needle. Then the fluid is sent to the laboratory for testing.

Why would a woman have an amniocentesis?
The fluid taken during an amniocentesis can be used to test for various birth defects and genetic conditions. These tests are usually very accurate and will usually be able to tell with a high level of certainty whether or not the baby has the condition or conditions that are being tested for. Amniocentesis is usually only offered if a woman is at higher than average risk to have a child with certain birth defects. The most common risk factors include:

• A mother who will be 35 or over at the time of delivery. As women get older there is a higher chance of having a child with a chromosome abnormality. The most common chromosome abnormality is Down syndrome, but there are other chromosome abnormalities as well. Some other chromosome abnormalities are milder than Down syndrome and some are more severe.
  
• A woman who has had a blood test, such as the maternal serum multiple marker screen, which suggests she is at higher than average risk to have a child with a chromosome problem or spina bifida.
  
• Physical birth defects or differences that have been seen on ultrasound. In these cases the amniocentesis can sometimes provide more information about the cause of these birth defects.
  
• Couples with a family history of certain genetic conditions. Many genetic conditions such as cystic fibrosis, muscular dystrophy, and some forms of mental retardation can be tested for by amniocentesis; however, these tests are not done on every woman.

If you know you carry a genetic trait or have a family member with a genetic condition, please talk to your health care provider or genetic counselor about whether testing may be available for this condition. Setting up genetic testing can be a complex process, so it is recommended that these issues be discussed before becoming pregnant, or as early in the pregnancy as possible.

Is amniocentesis safe?
Amniocentesis is a routine medical procedure, but it does carry a small risk. Occasionally, a woman will have bleeding or leakage of amniotic fluid after the procedure. Amniocentesis can cause miscarriage—about 1/200 women who have amniocentesis will experience a serious complication or miscarriage following the
procedure. Because ultrasound is used during the amniocentesis, the risk of damaging the developing baby and causing a birth defect is very small.

Is amniocentesis required?
The primary reason for having amniocentesis is to provide information for a pregnant woman, her family, and her health care provider. In most cases, a woman and her family will decide if they want amniocentesis based on the risks and benefits of the procedure. Sometimes, the information provided by the amniocentesis will be important to the care of the pregnancy. In such cases, a health care provider may recommend the amniocentesis, but the final decision about the amniocentesis is still made by the pregnant woman.

When is amniocentesis done?
The usual time to do an amniocentesis is around 15 weeks from the first day of a woman’s last period. In some cases, early amniocentesis can be attempted between 13 and 15 weeks. The advantage of early amniocentesis is that results are available earlier, but it may also have a slightly higher risk of complications. If you are interested in early amniocentesis, we encourage you to talk to your health care provider or to St. Luke’s Maternal Fetal Medicine staff.

What should I do to prepare for an amniocentesis?
It is generally not necessary to have a full bladder. However, if you are having an early amniocentesis it may be helpful to not empty your bladder starting 30 to 45 minutes before your appointment.

You may be more comfortable wearing a two piece outfit. Otherwise, no special preparation is necessary before your appointment.

What should I expect on the day of the amniocentesis?
Generally, a woman will meet with a genetic counselor before the amniocentesis. The counselor will review the risk(s) and benefits of the amniocentesis and answer any questions you may have. The genetic counselor will assist you with necessary paperwork, arrange for communication of results, and take a pregnancy and family history. If you are undecided about having an amniocentesis or if it is more convenient, the genetic counseling appointment can be scheduled several days or weeks before the day of the amniocentesis.

Prior to the the amniocentesis a brief ultrasound will be done to locate the best place from which to withdraw fluid. Ultrasound may also detect abnormalities in the fetus, but these are often hard to see at the point in pregnancy when amniocentesis is done. Therefore, you may wish to talk to your health care provider about having a thorough ultrasound done between 18 and 20 weeks.

Once the physician has determined the best place to put the needle, the area is cleaned and prepared. With the ultrasound on, the needle is inserted and the fluid removed. The needle is never placed through the belly button. The procedure itself takes under 10 minutes and the removal of the fluid takes about 2 minutes. Most women say the procedure is not painful; some will experience a feeling of pressure or cramping.

Can someone be with me during the amniocentesis?
Yes, in most cases your partner, friend, or family member can be with you. Because children may not understand the procedure and may find it frightening, we encourage you to make other arrangements for their care.

What should I do after the procedure?
At a minimum, a woman should avoid heavy lifting, strenuous activity and sexual intercourse for 48 hours after the procedure. In addition, bed rest may be suggested for the remainder of the day.

How accurate is the amniocentesis?
Amniocentesis is quite accurate (>99%) in detecting chromosome problems and open neural tube defects. However, the amniocentesis does not test for all birth defects. About 3-5% of babies are born with some kind of birth defect. Many tests can be done on the amniocentesis, but not all tests are right for all people. Before the amniocentesis, the genetic counselor will work with you to determine (based on your personal and family history) which tests will be done. Current technology does not allow us to test for all possible birth defects, so it is possible for a baby to be born with a birth defect that was not detected through the amniocentesis.

Occasionally, there will be technical problems with the sample. For example, not enough fluid may be taken or the cells from the amniotic fluid may not grow. In these cases, you will be told as soon as possible and be given the option of repeating the amniocentesis.

When and how will I receive my results?
You should expect to get results about 2 weeks after the amniocentesis. Typically, results will be given to you by telephone as soon as they are available. If you require special arrangements for getting your results, these can be made with the genetic counselor or nurse at the time of your appointment.

What happens if the amniocentesis shows that the baby has a birth defect?
Most results are normal, but if the testing shows that the baby has a birth defect, you will be provided with as much information as possible about the condition and your options. For some families, having this information helps them prepare for the birth of a child with special needs. Other families who learn of a serious birth defect may choose to end the pregnancy or to place the baby for adoption. Genetic counseling is available to help families learn more about their options and make the decision which is most consistent with their personal beliefs and values. We strongly believe each family has the right and the ability to make an informed decision, and it is the role of the genetic counselor and other health care providers to support them through this process.

Does insurance pay for amniocentesis?
In most cases, insurance covers the cost of amniocentesis at the same rate that it pays for other obstetric care. We strongly suggest you contact your insurance carrier prior to your appointment to determine the extent of your coverage.

What if I am not sure I want the amniocentesis?
You may wish to discuss this with your health care provider. In addition, if you are undecided about having the amniocentesis you may wish to meet with the genetic counselor several days or weeks before the time an amniocentesis would be scheduled. This visit will help you think through the issues relevant to your family and assist in your decision-making process. The goal of genetic counseling is to help you make the decision that is most appropriate for you based on your individual situation, beliefs, and values.

What if I still have questions ?
If you have more questions about amniocentesis, please discuss them with your health care provider. You may also contact St. Luke’s Maternal Fetal Medicine at (208) 381-3088.