Amniocentesis (15+ weeks) including Rapid FISH Result & Full Karyotype
An amniocentesis involves taking a small sample of amniotic fluid to determine the baby’s chromosomes. It is requested when there is heightened concern about Down’s syndrome or other chromosomal conditions either following a nuchal scan, a Harmony test, a previous affected baby, or simply for maternal reassurance.
The procedure is always carried out under the continuous guidance of an ultrasound scan to ensure that the fine needle is kept well away from the fetus.
This test carries a small, but important, risk of miscarriage (1%).
How is the test performed?
After discussion with our experienced fetal medicine consultant a scan is performed trans-abdominally by placing a probe on the abdomen and your tummy is cleansed with antiseptic. No local anaesthetic is given as the needle used is so fine it is narrower than the needle we would need to use to administer the local anaesthetic. After cleansing is complete the fine needle is inserted through your skin into the amniotic fluid around the fetus, avoiding the fetus and a small sample of fluid containing fetal cells is taken.
The procedure does not take long and women describe the sensation as mild discomfort rather than painful.
What does this package include?.
- An abdominal ultrasound scan to check the position of the fetus and placenta.
- A discussion about the scan findings or the findings of any other relevant medical/obstetric history or testing you may have had in this pregnancy.
- An amniocentisis performed under ultrasound guidance.
- A rapid PCR result (usually available in three working days) providing a result for Down’s syndrome (trisomy 21) and two other common chromosomal conditions Edward’s syndrome and Patau’s Syndrome(trisomies 18 and 13)
- A Full Karyotype (usually available two weeks after your test) providing information on all of the fetus’ chromosomes.
- Telephone follow up with an experienced midwife to discuss all low and high risk results and any question or concerns you may have.
How to prepare for your test
No preparation is required prior to this test. However we recommend that somebody accompanies you to your appointment.
One of the main risks of amniocentesis is miscarriage. This is estimated to occur in around 1% of pregnancies nationally after an amniocentesis.
An amniocentesis is uncomfortable rather than painful and you may feel slight cramping for a day or two afterwards. Some women describe feeling a pain similar to period pain, or feeling pressure when the needle is taken out.
Signs to look out for and who to call should you have any concerns after the test will be discussed with you during your consultation.
Occasionally it is necessary to perform a second test as the sample taken at the first doesn't culture in the lab. It is not always known why this happens and we cannot predict cases where this will happen.