Rubella in pregnancy: risks, blood tests and management

Why is rubella dangerous in pregnancy?

Rubella is a viral infection spread through the air. In adults, it causes a rash, fever, swollen glands and sometimes joint pain, but it often goes unnoticed.

During pregnancy, the virus can cross the placenta and infect the foetus. If this happens early, it can cause congenital rubella: cataracts, deafness, heart defects, growth restriction and neurological damage. Thanks to vaccination, these cases have become rare in France, but they have not disappeared. This is why a rubella blood test is part of the initial check-up in every pregnancy, described on our page Giving birth in Paris.

What is the risk to the baby at each stage of pregnancy?

The danger depends on when the mother is infected. A British study followed more than a thousand women with confirmed rubella during pregnancy (Miller et al., 1982):

In France, care is based on thresholds of 12 and 18 weeks of amenorrhoea (counted from the last period), and each situation is assessed by the prenatal diagnosis team. The key point: the first trimester is the critical period.

Reinfection in a woman who is already immune is possible but exceptional, and the risk to the foetus is then much lower.

How do I read my rubella blood test results?

The blood test looks for IgG antibodies, which show protection. In France, it is compulsory in early pregnancy unless you have a written result proving your immunity or two documented doses of vaccine.

• Positive IgG with no particular context: you are protected. No further tests are needed, and there is no point testing IgM.
• Negative IgG: you are not protected. Avoid contact with anyone who has a rash and report any contact or rash. A repeat test is done at around 20 weeks to detect an infection that went unnoticed, and vaccination will be offered after the birth, before you leave the maternity unit.
• Possible recent infection (rash, contact, unusual result): the laboratory repeats the test about two to three weeks later and analyses both samples together, tests for IgM and measures IgG avidity. High avidity points to a past infection.

IgM can persist for a long time or give false positives. A single result should never lead to a decision without the opinion of a specialist laboratory.

What should I do if I have been in contact with rubella while pregnant?

1. Tell your doctor or midwife quickly and give the date of the contact.
2. If your immunity is documented, the risk is minimal; no further steps are usually needed.
3. If you are not immune or your status is unknown, a blood test is done as soon as possible, then repeated about three weeks later to detect seroconversion (new antibodies).
4. If you develop a rash, a blood test and sometimes a mouth swab (to look for the virus) are carried out.

There is no antiviral treatment for rubella, and no effective preventive treatment after contact for pregnant women.

How is rubella managed during pregnancy?

A confirmed recent infection is managed by a multidisciplinary prenatal diagnosis centre. The couple receives full information and takes part in every decision.

• Infection before 12 weeks: the risk of severe abnormalities is very high. A termination of pregnancy for medical reasons may be requested by the couple; it is never imposed.
• Infection between 12 and 18 weeks: prenatal diagnosis may be offered to find out whether the foetus is infected. It relies on amniocentesis, carried out after 18 weeks and at least six weeks after the infection, with PCR testing for the virus, together with follow-up scans.
• Infection after 18 weeks: the risk of abnormality is very low; follow-up scans and an examination of the baby at birth are arranged.

A baby infected during pregnancy is followed up after birth, particularly for hearing and sight.

How can I protect myself from rubella before pregnancy and after the birth?

Vaccination is the only effective prevention. It uses the combined measles, mumps and rubella (MMR) vaccine, in two doses.

• Before pregnancy: any woman of childbearing age without proof of two MMR doses should be vaccinated. A pre-pregnancy consultation is a good opportunity to check your vaccination record.
• During pregnancy: MMR is a live attenuated vaccine and is contraindicated as a precaution. However, a vaccination given by mistake in early pregnancy is not a reason to end the pregnancy: no case of congenital rubella caused by the vaccine has been reported.
• After the birth: if you are not immune, you are vaccinated at the maternity unit. It is compatible with breastfeeding.
• Effective contraception is needed for 1 month after each dose, according to the current vaccine leaflets (the 2009 HAS document stated 2 months).

For all the vaccines recommended around pregnancy, see our article on vaccines during pregnancy. Other infections causing a rash are covered in chickenpox in pregnancy.

When should I go to the maternity unit urgently?

A rash with fever during pregnancy needs prompt medical advice, the same day, but do not walk into a shared waiting room without warning (risk of infecting other pregnant women). Call your doctor or the maternity unit first.

Some signs should not wait for your next appointment. Go directly to your maternity unit's emergency department (open day and night), at the unit where you are registered (Sainte-Félicité Maternity Unit or Clinique Sainte-Thérèse), if you have:

• any vaginal bleeding, even light;
• a leak of fluid, clear or coloured, from the vagina;
• regular or painful contractions before 37 weeks;
• fewer or no movements from the baby (once you usually feel them);
• a fever of 38 °C or more, shivering, or burning when passing urine with back pain;
• severe headaches, vision problems, pain under the right ribs or in the pit of the stomach, sudden swelling of the face or hands;
• severe or constant abdominal pain, a fall or a blow to the abdomen;
• intense itching of the palms and soles of the feet, especially at night.

If you feel faint, have heavy bleeding or very severe pain, call 15 (SAMU) or 112 in France, or your local emergency number.

Frequently asked questions

General information article: it does not replace a medical consultation. In an emergency, call 15 or 112 in France, or your local emergency number.