All about the amnio
WHAT IS IT?
Amniocentesis is a prenatal test where a sample of the amniotic fluid surrounding the baby is withdrawn. It’s mostly used for testing of genetic conditions, but can also be used to check if a baby’s lungs are ready in case you need to have a preterm delivery for any reason. WHEN AND HOW IS IT DONE FOR GENETIC CONDITIONS? Amniocentesis is usually done between 16 and 22 weeks of pregnancy. After the abdomen is cleaned with sterile fluid, and using a sonar as a guide, a needle is inserted through the abdominal wall into the uterus, and between 10 to 20ml (less than four teaspoons) of amniotic fluid is drawn up. When done for lung maturity, it is performed in the late third trimester.
HOW DOES IT WORK?
Our bodies are made up of thousands of cells which contain the genetic material. This is made up of 23 pairs of chromosomes which hold the genes responsible for everything about us – not only how we look, but everything about us, including how our bodies function. We naturally lose skin cells everyday (notice the ring around the bath and basin, or dry skin flaking off) and so does the unborn baby. A sample of the amniotic fluid contains the baby’s cells, and these are extracted and analysed in the laboratory.
WHO DOES THE AMNIOCENTESIS?
A skilled obstetrician, foetal medicine specialist, or an experienced radiologist.
DOES IT HURT? DO I HAVE A LOCAL ANAESTHETIC?
A local anaesthetic is not used, because the amniocentesis is relatively quick. You will feel the needle being inserted, and if the abdominal muscles are relaxed, it tends to be less painful. Women have described the sensation as “strange” when the fluid is pulled back into a syringe. After the procedure, you may feel lower abdominal pain similar to period pain, but this will pass. You can take paracetamol for any pain you may feel if you need to.
WHY IS TESTING DONE?
Amniocentesis is offered to women for the following reasons: • If the mother is over the age of 35 years, she has a higher chance of having a baby with a chromosome abnormality like Down syndrome or other chromosome abnormalities. • If abnormalities have been seen on any of her sonars. • If the parents are known “carriers” of a genetic condition where they have a chance to have an affected baby, like cystic fibrosis, sickle cell anaemia (common in people from central Africa) or thalassaemia (common in Greek and Indian communities).
• If one of the parents carries a “balanced” chromosomal rearrangement (the right amount of chromosomes, and the right amount of genetic material) but there is a risk to have a baby with an “unbalanced” rearrangement of chromosomes. • If the mom has had a positive first trimester screen, or positive second trimester screen. Remember that a positive screen does not mean that the baby has Down syndrome, it just means that the risk has been increased from the age related risk. This naturally raises the anxiety levels and an amniocentesis is the only way of knowing 100 percent if the baby is at all affected.
WHAT ARE THE RISKS?
As there is a needle inserted through the uterine wall and membranes there is a small risk of infection. The main risk is that of miscarriage and is the region of 0.7-1 percent. Although some doctors are more conservative than others, and some say you can carry on as normal, it is advisable to take precautions after the procedure to minimise this risk. So you should rest, not do any strenuous exercise and avoid sexual intercourse for a few days after the procedure. Be sure to have your amniocentesis performed by a qualified person to reduce risks. Although there is not extensive research on this, by inserting a needle into the womb, there may be a small chance of HIV positive blood mixing with baby’s.
WHAT SHOULD YOU LOOK OUT FOR?
If you have any severe cramping, or loss of fluid or blood, you need to go to your hospital or clinic immediately. Although this is very rare, complications and miscarriage associated with an amniocentesis usually occur within two weeks after the procedure.
HOW MUCH DOES IT COST?
In the state system, pregnant women are free patients, and the costs are covered by the hospital. In the private sector, there is a cost for the scan and procedure of approximately R2 600, the analysis of the chromosomes is R4 000 and the PCR is R2 000. If you discuss it with your medical aid, they should cover some of the costs, depending on your specific medical scheme.
IS THE TESTING ACCURATE?
The laboratories are very careful in their sorting and testing of samples, and there should be no chance of an error. It is very important to note that although the baby may not have a chromosomal abnormality, or other genetic conditions, there is no way of knowing for sure whether or not the baby may have a visual or hearing impairment or intellectual delay. It’s important that the midwife, doctor or genetic counsellor take a thorough genetic history to make sure, as best as they can.
PLEASE TAKE NOTE:
If you’re Rh-negative, it’s imperative that you have an anti-D injection after an amniocentesis – this will help prevent a build-up of Rh-positive antibodies which could affect your baby in future pregnancies. If you’re HIV postive and want an amniocentesis done, you must be on ARV treatment for at least two weeks prior to the test – please discuss the taking of ARVs with your doctor or midwife.