What is amniocentesis?
Amniocentesis involves the removal of a small amount of amniotic fluid from uterus to examine the fetal cells (skin cells) for chromosomal abnormalities. The cells in the amniotic fluid originate from the baby and so the chromosomes present in these cells are the same as those of the baby.
How is amniocentesis done?
A thin needle is passed through the maternal abdomen into the uterus to remove a small amount of amniotic fluid (15mL or 3 teaspoons of fluid). The procedure is performed under ultrasound guidance and the needle can be visualized at all times. The fluid is actually the fetal urine and is replaced within a few hours following the procedure.The procedure lasts less than 1 minute and afterwards we check that the fetal heart beat is normal.
What should I expect after amniocentesis?
For the first couple of 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 any problems. You may find it helpful to take simple painkillers like paracetamol 40 minutes before the procedure. If there is a lot of pain or bleeding or if you develop a temperature please seek medical advice.
When can I expect to get the results?
The results for Down’s syndrome and other major chromosomal defects are usually available within 3-4 working days (FISH or PCR test). For a full culture that would exclude rare defects, the villi need to be cultured first and a final result takes 2-3 weeks to obtain. We contact you with the results as soon as they are available.
Will the procedure need to be repeated?
In approximately 1% of cases the invasive test will need to be repeated because the results are inconclusive.
What are the risks associated with the test?
The risk of miscarriage due to amniocentesis in our unit is 0.3% (1 in 300 risk of miscarriage) over and above the spontaneous loss rate of 1% at 16-20 weeks. For the small risk of club feet and culture failure (due to immature fetal skin cells)from early amniocentesis, we do not perform amniocentesis before 16 weeks.