Amniocentesis and Chorionic Villus Sampling
About 30,000 pregnant women in the UK have either an amniocentesis or Chorionic Villus Sampling (CVS) to diagnose
What is an amniocentesis?
An obstetrician inserts a long thin needle into your abdomen to take a small amount of amniotic fluid for testing.
Using an ultrasound scan, the doctor will use a pocket of amniotic fluid that is away from your baby and
The sample of amniotic fluid can be tested for conditions such as:
Down’s Syndrome, Patau Syndrome and Edwards’ Syndrome
as well as genetic conditions such as Cystic Fibrosis and Sickle Cell Disease.
This can be performed after 15 weeks of pregnancy.
What is Chorionic Villus Sampling (CVS)?
The obstetrician will insert a long thin needle into your abdomen to take a small sample of placenta for testing. Using an ultrasound scan, the doctor will
keep the needle away from your baby and the placenta.
The sample of placenta is analyses to chromosonal make-up of your baby to identify Down’s Syndrome, Patau Syndrome and Edwards’ Syndrome.
This can be performed before an amniocentesis at 11-14 weeks.
Both procedures can take up to 20 minutes and a midwife will monitor you afterwards as you may experience some cramping. She will also listen to your baby’s heartbeat to make sure he is ok after the procedure.
You could be offered an amniocentesis or CVS if…
A screening test (your dating scan and nuchal scan) suggests your baby has a higher risk of having chromosomal problems
Your ultrasound scan shows a problem such as a heart defect, which may be a sign of a chromosomal problem
You have one or more relatives with a genetic disorder
You, or your baby’s father, has a greater risk of an inheritable condition, such as Sickle Cell Disease
You have had a previous pregnancy affected by a genetic abnormality
What are the risks?
These are both invasive procedures so there is a risk of infection (1 in 1000) and a risk of miscarriage (1 in 100 for amniocentesis and 2 in 100 for CVS)
You will be advised to take it easy for a day or two.
You may experience some cramping and you may leak some amniotic fluid from your vagina – this should stop after a day or so but see your midwife or go along to the nearest Pregnancy Assessment Unit if you are unsure or if something doesn’t feel right.
If you feel unwell, fluey or you experience contractions – get checked out by your midwife or at your
Pregnancy Assessment Unit.
The initial results take 3 days and the indepth results take 3 weeks.
The doctor will tell you more about when to expect the results and how you will receive them.
If the results identify a problem with your baby you will be able to discuss this with a fetal medicine obstetrician at the hospital to find out more about your
baby’s condition and to help you make a decision about whether you want to proceed with your pregnancy.
Antenatal Results and Choices (ARC)