Amniocentesis

Amniocentesis is usually the unborn , developing baby evaluate different chromosomes or genetic condition , a procedure that is done during pregnancy . Amniotic fluid surrounding the baby inside your uterus ( womb ) of a sample is taken using a fine needle . Test laboratories are fluid . Amniocentesis completed 15 weeks of pregnancy ( usually between 15-18 weeks) is presented . Amniocentesis is the most common reason given for a pregnant woman to their developing baby such as Down 's syndrome to see if there is a chromosome disorder . Complications including miscarriage with amniocentesis , a little bit of risk .

A note about DNA, genes and chromosomes

In most cells of your body you have 46 chromosomes arranged in 23 pairs. One chromosome from each pair comes from your mother and one from your father. Chromosomes are made of DNA. DNA stands for deoxyribonucleic acid. It is your genetic material and is found in the nucleus of the cells of your body.

Each of your chromosomes carries hundreds of genes. A gene is the basic unit of your genetic material. It is made up of a sequence (or piece) of DNA and sits at a particular place on a chromosome. So, a gene is a small section of a chromosome. Each gene controls a particular feature or has a particular function in your body. For example, dictating your eye colour or hair colour. Each gene is part of a pair. One gene from each pair is inherited from your mother, the other from your father. Humans have between 20,000 and 25,000 genes.

Why Is an Amniocentesis Performed?

Amniocentesis is performed to look for certain types of birth defects, such as Down syndrome, a chromosomal abnormality.

Because amniocentesis presents a small risk for both the mother and her baby, the prenatal test is generally offered to women who have a significant risk for genetic diseases, including those who:

• Have an abnormal ultrasound
• Have a family history of certain birth defects
• Have previously had a child or pregnancy with a birth defect
• Will be 35 or older at the time of delivery

Amniocentesis does not detect all birth defects, but it can be used to detect the following conditions if the parents have a significant genetic risk:

• Down syndrome
• Sickle cell disease
• Cystic fibrosis
• Muscular dystrophy
• Tay-Sachs and similar diseases

Amniocentesis can also detect certain neural tube defects (diseases where the brain and spinal column don't develop properly), such as spina bifida and anencephaly.

Because ultrasound is performed at the time of amniocentesis, it may detect birth defects that are not detected by amniocentesis (such as cleft palate, cleft lip, club foot, or heart defects). There are some birth defects, however, that will not be detected by either amniocentesis or ultrasound.

If you are having an amniocentesis, you may ask to find out the baby's sex; amniocentesis is the most accurate way to determine the baby's gender before birth.

An amniocentesis can also be done during the third trimester of the pregnancy to determine if the baby's lungs are mature enough for delivery, or to evaluate the amniotic fluid for infection.

How Accurate Is Amniocentesis?

The accuracy of amniocentesis is about 99.4%.

Amniocentesis may occasionally be unsuccessful due to technical problems, such as being unable to collect an adequate amount of amniotic fluid or failure of the collected cells to grow when cultured.

Does Amniocentesis Have Risks?

Yes. There is a small risk that an amniocentesis could cause a miscarriage (less than 1%, or approximately 1 in 200 to 1 in 400). Injury to the baby or mother, infection, and preterm labor are other potential complications that can occur, but are extremely rare.

What are my choices if the results are abnormal?

Deciding to have amniocentesis can be a very difficult decision and a very anxious time. However, most women who have amniocentesis will have a normal result. That is, the baby won't have the genetic problem that the test was looking for. But, before you go through amniocentesis, it is important for you to think through carefully what difference an abnormal test result would make to you. How would it be likely to affect your decision about whether or not to continue with the pregnancy?

Once you know the results, and if the results show a problem, you need to make a decision about what is best for you and the baby. This decision may be very difficult. You may find it helpful to talk things through with your GP, your midwife, your obstetrician, a paediatrician, a genetic specialist, a counsellor, etc. You may also wish to talk things through with your partner or family.

There is still time to terminate the pregnancy (have an abortion) after amniocentesis if you choose to. Sometimes after amniocentesis this may mean an induced labour. However, the type of termination will depend on how many weeks pregnant you are when you decide to end the pregnancy. You should discuss this with your doctor or midwife.

Equally, if the results of amniocentesis do show a problem, you may choose to continue with the pregnancy. With the knowledge of the results, you can start to prepare for the birth and care of the baby who is likely to have special needs. The baby may need special care immediately after they are born. For example, they may need surgery or some other procedure. Prior knowledge that the baby has a certain condition means that you can plan to give birth in a hospital where all of the appropriate facilities are available.

In rare situations, amniocentesis may show that the baby has a condition that is treatable. Occasionally, there may be the possibility that treatment can be given while the baby is still in your womb.

Further help and information

ARC (Antenatal Results & Choices)

73 Charlotte Street, London W1T 4PN
Helpline: 0207 631 0285 Web: www.arc-uk.org
A charity offering information and support to parents going through antenatal testing.

Down's Syndrome Association

Langdon Down Centre, 2A Langdon Park, Teddington, Middlesex TW1 9PS
Helpline: 0845 230 0372 Web: www.downs-syndrome.org.uk