What it's all about

The risks associated with an amniocentesis – one in 100 women miscarry as a result of the procedure – mean that it’s not routinely offered to all expectant moms. Yet, it’s a test that provides information – the diagnosis of Down’s syndrome, most commonly, and other chromosomal and genetic abnormalities – that cannot be definitively diagnosed any other way.

The thought of a long needle piercing the sacred amniotic sac and disturbing the precious bundle growing there made my heart race. Would it be painful? What if something went wrong and we lost our baby? These are the questions my husband, Scott, and I battled with when our foetal-medicine specialist told us our circumstances meant that we should consider having an amnio.

The assessments done at our 13-week ultrasound scan showed nothing untoward but, because of my age (our baby would be born just after my 35th birthday) and because we’d lost a previous pregnancy due to a genetic anomaly, our odds were elevated.

If your chances of having a seriously disabled child are greater than the risk of miscarriage, your fears are put into perspective very quickly. We decided to go ahead. We wanted science and numbers on our side. To be able to know and prepare was better than not knowing. It certainly helped that we trusted implicitly the specialist doing the procedure. I knew if anyone could limit the risks to my baby and myself, this doctor could.

An amnio is usually performed between 14 and 18 weeks, and many parents choose to have the amnio as soon as possible. We opted to delay ours to 16 weeks because waiting reduces the chances of miscarriage to one in 400. The procedure was not pleasant but it was not painful. My anxiety was all mental and emotional. When we left the doctor’s rooms, we stood still in the passage and I buried my face in my husband’s chest. The tears streamed unceasingly as the anxiety I had felt for the weeks leading up to the procedure lifted. The feeling of relief was matched only by the news a few weeks later that the results were clear. Now it was real; we were having a baby and she was perfect.

When to consider an amnio

An amnio is offered to moms who are at a greater risk of having babies with a genetic or chromosomal abnormality. That is if...

You’re having your baby later in life.

The risk of Down’s syndrome, in particular, increases with age. According to foetal medicine specialist Dr Linnie Muller, at 32, your risk is one in 480; at 35, it’s one in 270; by 38, it’s one in 133. By 42, it’s one in 46.

You have a close family member with a chromosomal or genetic condition.

You get an abnormal result in a first-trimester screening test, such as at the nuchal translucency test (measurement of fluid in the fold behind the neck).

Something suspicious is found in a routine ultrasound exam.

You’ve had a positive result for an abnormality from a previous amnio.

Choosing your test
Your amniotic fluid sample can be analysed in several ways.
Chromosome analysis: samples are cultured for three to four weeks. Fewer or more chromosomes than normal (22 pairs plus two sex chromosomes) usually indicate
a congenital (and or mental) abnormality.
FISH: only five specific chromosomes (the most common chromosomal disorders) are counted and it can take three to four days. It is 98 per cent accurate.
AFP: tests for excessive amounts of a protein, which indicates anomalies like spina bifida.
Specific genetic diseases: if there is a disease like cystic fibrosis or sickle cell in your family, you can test for this specifically.

Who can do an amnio?

“Not all gynaes should be doing amnios,” says Dr Ilse Erasmus, of the SA Society for Ultrasound in Obstetrics and Gynaecology (SASUOG). In SA, there are just a handful of appropriately trained specialists. The English guideline is that an ob/gynae should do 50 or more procedures under supervision in order to offer amniocentesis. It’s best to ask your gynae for a referral, call SASUOG on 012-347-3344, visit sasuog.org.za or the SA Society of Obstetricians and Gynaecologists (sasog.co.za) for a recommendation in your area.

The procedure
You may choose to have a local anaesthetic to numb your abdomen but this injection may be more painful than the procedure itself. Your doctor will then use ultrasound to pinpoint a pocket of amniotic fluid that is a safe distance away from the baby and the placenta. Using the ultrasound as a guide, the doctor inserts a thin needle through the abdomen and uterus into the amniotic sac. A small amount of amniotic fluid is withdrawn and the needle is removed. The doctor then uses ultrasound to check the foetal heart rate is normal. It takes between 20 and 30 minutes.

Things to think about...

• Amniocentesis conclusively excludes chromosomal and genetic abnormalities.
  
• Providing your test is performed by a specialist with ultrasound guidance, injury to the foetus is extremely rare.
  
• You will need to rest for 24-48 hours following the test.
  
• You should avoid strenuous exercise for at least a week, preferably two, after your amnio.
  
• You may experience cramps, slight leakage of fluid or light spotting. These are normal and are not dangerous. Contact your foetal-medicine specialist if you’re concerned or if you develop a fever.
  
• Things can go wrong: bleeding and infection are the most common reasons for miscarriage after amniocentesis.
  
• You should not have an amnio while you have a cold, flu, fever or an infection of any kind, as this increases the risk.
  
• The procedure may not work or the cells may not culture; your test will have to be repeated to get a result.
  
• Make sure your doctor knows your blood type. If you are rhesus negative, he/she will take precautions to avoid harm to the foetus.
  
• In HIV+ mothers, the virus can be transmitted to the baby during amniocentesis.
  
• Before your appointment, inform the doctor of any medication you’re taking, including vitamins. Blood-thinning medication, for example, should be stopped several days in advance of the test.
  
• Counselling is available and recommended to help you make a decision about how to proceed should you get abnormal results back.