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What is amniocentesis?

Amniocentesis FAQs

What Is Amniocentesis?

Amniocentesis is a test usually carried out to examine a baby’s chromosomes, most commonly in search for Down’s Syndrome. Amniocentesis is always voluntary and parents decide if they wish to choose to have this test. The information below may help you to decide whether or not to have this test.

Amniocentesis is the withdrawal of a small amount of fluid from around the baby (amniotic fluid). Cells from the baby’s skin and bladder are in the fluid and can be grown in the laboratory for chromosome analysis. Chromosomes are tiny microscopic packages present in every cell of the body. Normally in each human cell, there are 46 chromosomes. A missing or extra chromosome causes many changes in the way an unborn baby develops. Amniocentesis can detect Down’s Syndrome (which is caused by an extra no.21 chromosome), other chromosome abnormalities and certain genetic conditions when there is a family history of such a disease

How is amniocentesis performed?

Amniocentesis is generally performed from 15 weeks gestation up to the date the baby is due. An ultrasound scan will be done first to check the position of the baby/placenta and to find a pocket of amniotic fluid. The skin on the mother’s abdomen (tummy) is cleaned with antiseptic fluid and a very fine needle is passed through the abdomen and into the womb. A small amount of fluid around the baby (amniotic fluid) is withdrawn. The needle is carefully watched with the ultrasound scan to ensure that it is in the correct position.

The test lasts for 2-3 minutes and afterwards, the baby’s heartbeat is checked. Local anaesthetic is not usually used as the insertion of the anaesthetic is often more uncomfortable than the test itself. Occasionally it may be necessary to pass the needle into the abdomen a second time. If your blood group is Rhesus negative you will require an injection of Anti-D to prevent blood incompatibility developing between you and the baby as a result of the amniocentesis test.

What should I expect after amniocentesis?

For the first few days, you may experience some abdominal discomfort, period-like pain or a little bleeding. These are relatively common and in the vast majority of cases, the pregnancy continues without a problem. You may find it helpful to take some simple pain relief like paracetamol (this is safe in pregnancy) and rest for a few hours.

When can I expect to get the results?

Results of the test are usually available in 2-3 weeks, this is because the cells have to grow before they can be examined. After the amniocentesis arrangements will be made to contact you with the results as soon as they are obtained from the National Genetics Centre Our Lady’s Hospital, Crumlin.

Most people are happy to receive the results over the phone but if you wish to come and obtain the result in person this can be organised. The full result will also tell whether you are expecting a boy or girl – so you may want to give some thought whilst awaiting the result as to whether or not you would like to have this information.

What are the risks associated with amniocentesis?

One in one hundred women who have an amniocentesis test will experience a miscarriage. There are no ways of predicting who will miscarry. For Down’s Syndrome, the amniocentesis result will clearly state whether the baby is affected or not, with a high degree of accuracy (99%).


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What Our Patients Say

Gráinne Macken

This is my second visit to Merrion Fetal, I was very pleased on both occasions. Lovely quiet waiting room, appointment was on time. The 20-week scan is very detailed we enjoyed watching our baby on the large TV screen. We got some beautiful photos. The nurse was very pleasant and talked us through all the measurements and anatomy. I would highly recommend this scanning clinic.”

Áine Gibney

I had the best experience at the Merrion Fetal Health clinic for my 20-week big scan. The staff were so friendly and so nice and the lovely lady who did my ultrasound scan was amazing. She was so thoroughgoing to absolutely everything and gave me such reassurance on how my baby was growing and developing. I would recommend any Mother to be to attend here if you are looking for a comfortable, reassuring and super pleasant experience.”

Linda O'Sullivan

Highly recommend! We had an early scan due to a little scare at the start of pregnancy and then another at 12 weeks to make sure all was good again. Helen who was scanning on both days was fantastic. We felt totally relaxed and un-rushed while she took her time finding the best angle of baby to get us the clearest pictures as keepsakes all while making sure everything was perfect with baby. She reassured us throughout and I can honestly say it was the best money we ever spent getting both scans done.

Please let Helen know we are 18 weeks now and flying along Highly recommend!



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All articles on the blog and website are intended as information only. Please do not consider any of the information provided here as a substitute for medical advice. At all times seek medical advice directly with your own doctor and medical team.


This website was formerly Merrion Fetal Health. The clinic has undergone a rebrand and is now known as Merrion Ultrasound.