I have been offered a blood test for viruses in pregnancy

Blood tests for antenatal infections

Why have I been offered a blood test?

A number of infections are known to have an effect on a baby’s growth and development if they cross the placenta and infect them in the womb.

A blood test to look for common infections is offered to mothers if their baby has been estimated to be smaller than expected on an ultrasound scan or sometimes when the baby has another structural concern noted during an ultrasound scan. It is important to understand that for most women who have a blood test to check for infections, the results are normal.

If infection is identified we would be able to offer further input in your care and in many cases there are treatments which can help reduce the impact on the baby.

Which infections will be tested for?

The blood test can check for recent or past infections for a number of different diagnoses in the mother. The specific infections tested for will depend on the findings of your ultrasound scan. These may include:

Cytomegalovirus (CMV): This is a common virus that usually causes mild or no symptoms in adults. In most cases the virus does not cause problems in the baby, however babies born with CMV, may have complications such as hearing loss, visual impairment, learning difficulties and epilepsy.

Toxoplasmosis: Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. Like CMV, most people will have few or no symptoms. Toxoplasma infection in fetus and neonate is very rare, and usually follows infection either during pregnancy or in the few weeks just before pregnancy occurs. Like CMV not all babies are affected, although potential complications may occur.

Syphilis: This is a bacterial infection that is most commonly transmitted via sexual contact. Syphilis can pass from mother to baby during a pregnancy and if left untreated can result in miscarriage, still birth, low birth weight and other medical problems. Treating as early as possible in pregnancy results in the best outcomes for babies. You will previously have been offered testing for syphilis by your midwife early in pregnancy. Repeat testing in some situations is however recommended.

Rubella: This is a disease caused by a virus, which spreads in coughs and sneezes. It is very rare in the UK due to the childhood vaccination programme, however if infection does occur during pregnancy, it can cause miscarriage, hearing or visual problems or problems with development of the baby’s brain or heart.

Parvovirus B19: Also known as Slapped Cheek Syndrome. In many cases, infection with parvovirus B19 during pregnancy does not cause problems in the baby. However, it may sometimes cause miscarriage or anaemia in the baby.

What happens if a recent infection is confirmed in the blood test?

In most women, it is very likely that the blood test will be reassuringly normal.

If the blood test suggests a recent infection in you or if the timing of a past infection is uncertain, the result will be reported to your doctor. In some situations more tests have to be performed on a previous blood sample taken earlier in pregnancy, or a further blood sample may be required. If tests confirm a recent infection in you this does not necessarily mean that the baby also has the infection. You will be contacted and offered to attend the Fetal Medicine Department at the RVI for a further ultrasound scan, counselling and possibly further tests of the pregnancy.

Can I decline having the blood test?

Having this test is entirely voluntary. If you decline, you will still be offered further follow up with your obstetrician and more antenatal ultrasound scans. In some situations (depending on the findings on your ultrasound scan) your doctor may suggest that the neonatal team review your baby after birth. If you would like more time to decide if having the blood test is something you wish to do or if you would like more information, please ask to speak to the doctor or midwife in clinic.

For further information

For further information please speak to the doctor or midwife in clinic.

Another helpful charitable resource is Antenatal Results and Choices, 0845 077 2290 or 0207 713 7486 via mobile.