Diagnostic tests in pregnancy

If your screening tests show a 'higher chance' result for sickle cell disorder, thalassaemia or Down's syndrome, you'll be offered further diagnostic tests to confirm if your baby has the condition. You'll also be offered these tests in some other circumstances.

These tests aren't completely safe and won't be offered to everybody.

Chorionic villus sampling (CVS)

CVS involves removing and testing a small sample of cells from your placenta (the organ linking your blood supply with your unborn baby’s). It's usually only offered in a specialist centre.

CVS is offered from 11 - 14 weeks of pregnancy.

How the test's done

While many women find this procedure uncomfortable, it shouldn't be painful.

To do the test:

1. an obstetrician will guide a fine needle through your abdomen or, in rare cases, through your cervix with the help of an ultrasound scan
2. they'll take a small sample of tissue from the placenta
3. they'll analyse the sample in the laboratory and count your baby's chromosomes

2 out of every 100 samples won't produce a clear result. If this happens you may be offered further tests.

For every 100 women who have CVS, 1 or 2 will miscarry. The health professional taking care of you can tell you more about the miscarriage rates after CVS in your hospital.

More about CVS

Amniocentesis

Amniocentesis involves removing and testing a small sample of cells from your amniotic fluid (the fluid surrounding the foetus in your womb). It usually takes about 10 minutes.

Amniocentesis can be done after 15 weeks of pregnancy.

How the test's done

While many women find this procedure uncomfortable, it shouldn't be painful.

To do the test:

1. an ultrasound scan will be performed to check the position of your baby in the womb
2. an obstetrician will then insert a fine needle through your abdomen into your womb
3. they'll take a sample of fluid surrounding your baby (called 'amniotic fluid')
4. they'll analyse the sample in the laboratory and count your baby's chromosomes

1 out of every 100 samples won't produce a clear result. If this happens you may be offered further tests.

For every 100 women who have amniocentesis, 1 will miscarry. The health professional taking care of you can tell you more about the miscarriage rates after amniocentesis in your hospital.

More about amniocentesis

Aftercare

For a day or two afterwards you may have some discomfort in your lower abdomen, this is normal.

If this happens, ask your pharmacist to recommend pain relief which may help.

You should take things easy and avoid strenuous exercise. If discomfort persists, contact your midwife.

Test results

In most cases, further tests don't find any health issues or conditions. However, if they do, what happens next will depend on the issue or condition.

You may be offered further tests and monitoring throughout your pregnancy.

Some health issues may turn out to be less serious and may get better on their own.

Chromosome variation

If the test finds a chromosome variation, such as Down's syndrome, your midwife or obstetrician will talk to you about what it means and the options you have.

It’s okay to ask lots of questions and be honest about how you’re feeling.

Support for decisions

If tests find that your baby has an issue or condition that’s very serious, your midwife or obstetrician will discuss options which may include:

• having a termination
• preparing for the birth of a seriously ill baby

Whatever your test results find, healthcare professionals will give you time, information and support to make decisions that feel best for you and your baby.

There'll be no pressure to influence you in your decision - healthcare professionals will provide you with help and support whatever you decide.

They may also arrange support from other organisations which specialise in supporting babies and families.

Referral to the fetal medicine team

If you're offered further tests, the health professional taking care of you will give you more information and may refer you to the fetal medicine team. This is a team that includes a specialist doctor, midwife and other health professionals.

Members of this team may offer you further tests and provide information and advice about you or your baby . This could be in another hospital and they'll usually give you an appointment within a few days.