After amniocentesis has been carried out, the sample of amniotic fluid will be sent to a laboratory for testing.
If rarer conditions are also being tested for, it can take 3 weeks or more for the results to come back.
You can usually choose whether to get the results over the phone, or during a face-to-face meeting at the hospital or at home.
You'll also receive written confirmation of the results.
Amniocentesis is estimated to give a definitive result in 98 to 99 out of every 100 women having the test.
But it cannot test for every condition and, in a small number of cases, it's not possible to get a conclusive result.
Many women who have amniocentesis will have a "normal" result. This means that none of the conditions that were tested for were found in the baby.
But a normal result does not guarantee that your baby will be completely healthy, as the test only checks for conditions caused by certain genes and it cannot exclude every condition.
If your test result is positive, your baby has 1 of the conditions they were tested for.
In this instance, the implications will be fully discussed with you and you'll need to decide what to do next.
If the test finds that your baby will be born with a condition, you can speak to a number of specialists about what this means.
These could include a midwife, a doctor who specialises in childrens' health (consultant paediatrician), a geneticist and a genetic counsellor.
They'll be able to give you detailed information about the condition to help you decide what to do, including the possible symptoms your child may have, the treatment and support they might need, and whether their life expectancy will be affected.
A baby born with 1 of these conditions will always have the condition, so you'll need to consider your options carefully.
Your options are to:
This can be a very difficult decision, but you do not have to make it on your own.
As well as discussing it with specialist healthcare professionals, it can help to talk things over with your partner and speak to close friends and family.
You can also get support and more information from charities like: