Pregnancy Care: Invasive Tests

What do they involve?

These are diagnostic tests that are performed to examine the chromosomes of the baby. The principal concern for most women undergoing these tests is the potential risk of miscarriage, which is approximately 0.5 - 1% for the following procedures.

There are two types of invasive test which can be carried out.

Chorionic Villus Sampling (CVS)

This is performed from 11 weeks gestation and involves the removal of a small sample of placental tissue. Local anesthetic is injected to numb the skin and a fine needle is inserted through the abdomen into the placenta. An ultrasound scan is performed throughout the procedure to guide the needle accurately and check the baby's heart rate. The potential risk of miscarriage is approximately 1%.

Amniocentesis

This is performed from 14 weeks. A fine needle is passed through the abdomen and amniotic fluid removed from around the baby. Again an ultrasound scan is performed to guide the needle accurately. The potential risk of miscarriage is approximately 0.5%.

Results

The results of these types of invasive testing check the chromosomes of your baby. The most common chromosomal abnormality excluded by invasive testing is Down's Syndrome (Trisomy 21). These tests will tell us the gender of your baby. The results are available in 2 stages. The preliminary result is available after 48 hours and the final result after 10 - 14 days. We will contact you with these results and send a copy to your referring doctor. In the event that the result is not normal you will be fully counselled as to the implications and a referral to other clinicians. Throughout the whole process we will liaise closely with your Obstetrician or GP.