Amniocentesis is a diagnostic test that is performed on pregnant women at around 16 -18 weeks of pregnancy. The test involves the withdrawal of a small sample (approximately an egg cupful of amniotic fluid) from around the baby, which is then analysed in a laboratory for signs of chromosomal abnormalities, such as Down's Syndrome.
The doctors who perform the test are very experienced and can usually obtain a suitable sample of fluid on the first attempt. Very rarely, a second test will need to be conducted, but it is advisable to wait for at least a week before performing a second needle insertion.
Again, in a very small number of cases, a second test may need to be performed if, for example, the cells within the fluid do not grow sufficiently in the laboratory, meaning that it is not possible for them to be examined.
What Are The Reasons For Performing an Amniocentesis?
§If you are 35 or older, you may be advised to have an amniocentesis because of the higher risk of giving birth to a child with a chromosomal problem, such as Down's Syndrome
§If you have already given birth to a child with a genetic disorder or a neural tube defect, such as Spina Bifida, you will be offered the test because your chances of having a child with a similar disorder will be greater than if you have already given birth to healthy babies
§The test can determine the sex of the baby, which can be important when assessing the likelihood of diseases that only affect one sex. Haemophilia, for example, only affects males, so if there is a family history of this disease, it may be important for a couple to find out whether their child is male or female.
§In late pregnancy, an amniocentesis is sometimes performed for a number of reasons, one them being to determine the lung maturity of the foetus
Are There Any Situations Where An Amniocentesis Would Be Inadvisable?
Yes. There are some women who, for whatever reason, are in a high-risk category and should not have an amniocentesis. However, these reasons will be discussed with your counsellor or consultant. For the sake of this article, we will assume that we are referring, for all intents and purposes, to a normal pregnancy.
How Accurate Are The Tests?
The tests that are performed on the sample of amniotic fluid are very accurate. There is a 99% accuracy in detecting Down's Syndrome and a 90% accuracy in detecting other conditions such as Spina Bifida and less common chromosomal problems.
It is important to remember that not all genetic disorders and diseases can be detected via amniocentesis, but a good test result still means that you have a high chance, as most women have anyway, of delivering a healthy baby.
Will the actual procedure harm my baby?
The thought of a needle penetrating the abdomen and, especially, invading the area surrounding your precious baby, can be alarming to many women. However, when my amniocentesis was performed during my last pregnancy, the ultrasonographer informed us that the needle was surrounded by a very thin plastic tube and that once the needle had penetrated the amniotic cavity, the sharp bit would be withdrawn, leaving only the minute, plastic tube into which the fluid would be withdrawn. She reassured us that even if the baby should reach out and grab the tube, she would not be harmed.
Does it hurt?
A local anaesthetic is generally given prior to the needle being inserted into the abdomen. However, the insertion of the needle may cause some temporary, local discomfort, but should not be any more painful than any other type of injection. Obviously, the amount of discomfort felt will vary from woman to woman and may depend upon the individual's own pain threshold or, indeed, their state of mind. If you think that something is going to hurt, then you will naturally tense up and you will inevitably feel more pain and vice versa.
It is normal to feel slight menstrual-like cramps for a few hours following the procedure, but naturally the more tense and anxious you are, the worse the pain is likely to be. Some women suffer no pain at all.
What are the chances of miscarrying following the procedure?
A very small number of women may miscarry following an amniocentesis and statistics show that this risk is 1 in 150 to 200. However, two to three percent of women who do not have amniocentesis will naturally miscarry after sixteen weeks anyway. It is difficult, therefore, to determine whether a miscarriage following amniocentesis has been caused by the procedure or whether it would have occurred anyway, even if the procedure had not been performed. It has hence been concluded that most miscarriages following amniocentesis are not due to the procedure itself.
What Should I Do Immediately Following The Amniocentesis?
Firstly, go home and rest!!! Secondly, make sure that you drink 2-3 litres of fluid (preferably water) within the same number of hours following the procedure. This is to help replace the amniotic fluid that has been withdrawn. This may seem odd, when only an egg cupful of fluid has been removed, but most of the liquid that you drink will, of course, come straight out the other end!!
Resting for a couple of days and then taking it easy for a week following the amniocentesis should be sufficient, following which you may resume your normal everyday activities.
What Are The Warning Signs Of A Possible Miscarriage?
This is a depressing and worrying thought to entertain, yet nevertheless one that needs to be covered.
If you should suffer from any bleeding or fluid loss from the vagina, whether or not it is accompanied by abdominal cramps, go to bed and call the doctor immediately. It does not necessarily mean that you will lose the baby, because many women suffer from light bleeding during pregnancy for a variety of reasons. However, in these situations, staying in bed, resting completely and seeking medical advice is the best possible course of action.
Can I Choose Not To Know The Sex Of My Baby?
Yes. When you complete the initial forms, you will be asked whether or not you wish to know the sex of your baby. If you choose not to know, this information will be omitted from the letter that you receive from the testing laboratory.
How Long Do The Test Results Take To Come Through?
This can vary depending on the hospital, the area and the country in which you live. Nevertheless, in most cases, the test results take between two to three weeks, sometimes less and sometimes more. However, if a problem is detected, you will be contacted fairly quickly by the hospital and this will almost inevitably be by telephone. Generally, if you receive a letter through the post from the testing laboratory, it is a sign that the test results are normal.
What Happens If The Test Results Are Abnormal?
As with miscarriage, this is not a subject that any parent wishes to dwell upon, but it is one that is always at the back of every parent's mind before the results come through.
Prior to having the amniocentesis, your consultant or counsellor will have reviewed the options available to you.
Fortunately, in most cases, the baby is perfectly normal and healthy, but a small number of babies will have serious defects (even in younger mothers) that may result in the parents' choice to terminate the pregnancy. This is never an easy decision to make, particularly at a stage of pregnancy (around 20 weeks) when you will already have felt the baby move and when the foetus is moving towards a stage of viability. However, there are many factors to be considered, including the seriousness of the defect, whether it is a condition that will be incompatible with life anyway (i.e. the baby would be stillborn or die shortly after birth) and the quality of life that the child could be expected to have, should he or she survive.
My Personal Experience of Amniocentesis
I have absolutely no regrets about having an amniocentesis and would not hesitate to have the procedure done again. By the time we received the results informing us that our daughter was fine, I was 18 weeks pregnant. That meant that I had over five months when I could enjoy my pregnancy, knowing that all was well, knowing the sex of my baby, being able to talk to her by name and being able to plan accordingly.