The Mummy Guides - What tests will I be offered and when?

Certain tests are available throughout your pregnancy to check your baby for genetic problems such as Down’s syndrome and spina bifida.

These may be offered if you have had a blood test that suggests the possibility of problems, if you are over 35, or have a family history of certain conditions.

They’re not routinely performed because they all carry a slight risk of miscarriage. This can make the decision to have one difficult, but your midwife, obstetrician and hospital counsellor are there to help you.

Here’s the lowdown on what the procedures involve and when you may be offered them.

What you may be offered and when

CVS (10-14 weeks)
Chorionic villus sampling is usually available to women who are over 35 (because the risk for Down’s increases with age) or who have a family risk of inherited disorders. An average of two in every 100 women miscarry as a direct result of CVS.

What will happen to me?
Using an abdominal or vaginal ultrasound scan to locate your placenta, your doctor will carefully insert a needle though your abdomen to extract a fragment of the placenta so that cells can be analysed; these are full of genetic information that can reveal the chromosomal make up your baby (including the sex). Results are usually available within 10 days.

After the test
Some tummy cramping is normal, and you may notice a little blood loss from the vagina in the first 24 hours. It’s important to rest afterwards. If you notice bleeding or a clear fluid leaking from your vagina, or if you have contractions or feel shivery (like you’re going down with flu) contact your doctor or midwife immediately.

Did you know?
When carrying out these diagnostic tests, some hospitals have lower miscarriage rates than others. You can ask your hospital what their miscarriage rate is before you agree to the procedure.


Amniocentesis  (from 15 weeks)
This test is similar to CVS, but cannot be carried out until 15 weeks and involves taking a sample of amniotic fluid rather than the placenta.

You will be offered it if the result from a screening test such as a blood test, ultrasound or nuchal scan indicates that your baby is at a high risk of having chromosomal problems.

The miscarriage risks of amnio are slightly lower than those of CVS; around one woman in 100 miscarries after having amniocentesis.

What will happen to me?
As with CVS, your doctor will use a long, hollow needle to withdraw a small amount of amniotic fluid (around 2 tbsps). This contains cells and miro-oganisms that can be analysed and used to answer questions about your baby’s health.

After the test
Once the needle is out, you may get stomach cramps. A midwife will monitor you for a while to check that you’re not having any contractions, and listen to your baby’s heartbeat to ensure all is ok before you go home.

It’s important to rest afterwards. Results usually take three weeks to come back, but some laboratories have sophisticated equipment which can get results in ten days.

Does it hurt?
Most women find CVS and amniocentisis uncomfortable rather than painful, and describe feeling period-type pains. If you’re worried about the needle, you can ask to have your tummy numbed with a gel or cream.

If you have a transvaginal scan, it may feel as if you are having a smear test, and if your scan was on your tummy, it can be sore afterwards from the pressure.


Cordocentesis (after 18 weeks)
Another method of diagnostic testing is sampling the fetal blood from the cord. This is now mainly used to identify conditions such as fetal blood disorders or infection: if these are diagnosed, your baby can be given a blood transfusion using the same needle. There is a miscarriage risk of between one and two per cent.

What will happen to me?
The technique is similar to amniocentesis and CVS except that the aim is to obtain a sample of fetal blood. Using ultrasound for guidance, a needle is passed through your abdomen to obtain a sample of blood from your baby. This is sent to a laboratory, and a full chromosome result is usually available within 72 hours.



Mum’s top tip
"I’d recommend making sure you have someone with you when you have one of these tests. After my CVS, I felt weak and tearful. I was really glad I had my husband and mum to look after me."
Betty Pearce, 37, 20 weeks pregnant